Lockdown

A lockdown is a restriction policy for people or community to stay where they are, usually due to specific risks to themselves or to others if they can move and interact freely. The term "stay-at-home" or "shelter-in-place" is often used for lockdowns that affect an area, rather than specific locations.
The term is used for a prison protocol that usually prevents people, information or objects from leaving an area. The protocol can usually only be initiated by someone in a position of authority.
A lockdown can also be used to protect people inside a facility or, for example, a computing system, from a threat or other external event. In buildings doors leading outside are usually locked so that no person may enter or exit. A full lockdown usually means that people must stay where they are and may not enter or exit a building or rooms within it, needing to go to the nearest place designated safe if not already in such a place. 
The first lockdown implemented during COVID-19 as a preventive measure was in Wuhan in January 2020.
Types.
Procedures for using both emergency and preventive lockdowns must be planned.
Preventive lockdown.
A preventive lockdown is a preemptive action plan implemented to address an unusual scenario or a weakness in system to preempt any danger to ensure the safety and security of people, organisation and system. The focus for preventive actions is to avoid dangers and risks arising from the nonconformity to the normal circumstances, but also commonly includes improvements in efficiency.
Preventive lockdowns are preemptive lockdowns to mitigate risk. Most organisations plan for the emergency lockdowns but fail to plan for other situations that might quickly degrade to dangerous levels. These protocols must be based on the type of threat, and should be kept simple and short for quick learning and implementation, and flexible enough to handle several scenarios. This allows administrators more options to choose from which are easier to use in various scenarios. For example, in case of a loud scene by a parent or an unarmed petty thief being chased by the police through the school playground, this flexible procedure allows school administrators the flexibility to implement a more limited lockdown while teaching in school continues, thus eliminating need for complete emergency lockdown, disruption and delays in resumption of teaching, etc. The consequences of not having procedures to implement such lockdowns is that the situation might quickly escalate where there could be loss of human lives.
Emergency lockdown.
Emergency lockdowns are implemented when there is imminent threat to the lives or risk of injury to humans, for example, a school's emergency lockdown procedures must be kept short and simple to make them easier to use under real life crisis conditions. Simple procedures can be easily taught with periodic lockdown drills instead of lengthy training.
In epidemics and pandemics.
Lockdowns can limit movements or activities in a community while allowing most organizations to function normally, or limit movements or activities such that only organizations supplying basic needs and services can function normally.
2009 swine flu pandemic.
A lockdown was implemented in Mexico from April 30 to May 5, 2009 due to the 2009 swine flu pandemic.
COVID-19 pandemic.
During the COVID-19 pandemic, the term lockdown was used for actions related to mass quarantines or stay-at-home orders. The first lockdown during the pandemic was implemented in Wuhan on January 23, 2020. By early April 2020, 3.9 billion people worldwide were under some form of lockdown—more than half the world's population. By late April, around 300 million people were under lockdown in nations of Europe, while around 200 million people were under lockdown in Latin America. Nearly 300 million people, or about 90 per cent of the population, were under some form of lockdown in the United States, and 1.3 billion people have been under lockdown in India.
The lockdown in the Philippines started on 14 March 2020 and is one of the longest and strictest lockdowns with varying levels of community quarantine being imposed on all major islands and cities. Similarly the lockdown in South Africa started on 27 March 2020 and progressed through various levels. It is also one of the strictest lockdowns in the world with cigarettes and alcohol banned throughout.
Climate change.
Lockdowns could be implemented in the near future in response to the effects of climate change. Measures taken under a "climate lockdown" could include governments limiting the use of private vehicles, banning consumption of red meat, imposing energy conservation measures, and forcing fossil fuel companies to stop drilling. According to economist Mariana Mazzucato, "To avoid such a scenario, we must overhaul our economic structures and do capitalism differently."
Typical scenarios.
Schools.
Lockdown procedures vary by site and country. Generally, a lockdown means that interior and exterior doors are locked, and all students and staff must remain in their location from the time the lockdown is announced. In some locations, windows are covered, and students stand at the back of the classroom or away from windows.
Since the Columbine shooting in 1999, lockdown procedures in schools have been changing. Some schools direct teachers to continue with standard procedures while remaining quiet, while some recommend an active approach against threats.
Prisons.
In prisons, the term "lockdown" can be defined as a course of action to control the movement of inmates. Confining all prisoners, except workers, to their cells until the end of the day is an example of a "lockdown period" in a corrections schedule. However a "full lockdown" is used when all prisoners are locked in their cells to prevent prison riots or unrest from spreading or during an emergency.
Hospitals.
In US guidelines, occasions for preventing entry into a hospital may include: power failure, earthquake, flooding, fire, bomb threat, hostage crisis and active shooter. Occasions for preventing both entry and exit from a hospital may include: external contamination, civil disturbance and abduction of an infant or child.
Lean manufacturing process.
In manufacturing, the term "lockdown event" refers to a continuous improvement initiative in which manufacturing in a specific area (typically a cell or specific piece of machinery) is halted in order to contain, and determine, what are the issues that are preventing the manufacture of goods from meeting quality specifications. During the "lockdown event" a multi-disciplinary team reviews the specific area's manufacturing processes, tooling and machine condition, to find the root cause(s) of the problem(s). Once changes to the process, or machine repairs that may include adjustments or replacement are effected, a sample run is initiated and evaluated. If the results of the validation are within the required specifications, the area lockdown is lifted and production is resumed. Follow-up sampling is conducted subsequently to ensure continuity of the lockdown results.
Historical events.
In the wake of the September 11 attacks (2001), a three-day lockdown of American civilian airspace was initiated.
At the University of British Columbia (UBC) on January 30, 2008, an unknown threat was made, and the Royal Canadian Mounted Police (RCMP) issued a lockdown order on one of the buildings on campus for six hours, cordoning off the area. A campus alert was sent via email to everyone affiliated with UBC, while those in the building remained locked in it.
On April 10, 2008, two Canadian secondary schools were locked down due to suspected firearm threats. George S. Henry Academy was locked down in Toronto, Ontario at approximately 2:00 p.m. The Emergency Task Force (TPS) were contacted and the lockdown lasted for more than two hours. New Westminster Secondary School was locked down in New Westminster, British Columbia at approximately 1:40 p.m. The Emergency Response Team (ERT) was called, and the school was under lockdown until 4:30 p.m. Due to the size of the school some students were not able to leave until 7:00 p.m.
On April 19, 2013, the entire city of Boston, US was locked down and all public transportation stopped during the manhunt for terrorists Dzhokhar and Tamerlan Tsarnaev, the perpetrators of the Boston Marathon bombing, while the town of Watertown was under heavily armed police and SWAT surveillance, and systematic house-to-house searches were carried out.
In Belgium, its capital Brussels was locked down in 2015 for days while security services sought suspects involved with the November 2015 Paris attacks. Later in 2015, a terror threat caused the 2015 Los Angeles Unified School District closure.
In August 2019, the Indian government imposed a lockdown on Jammu and Kashmir after the revocation of the special status of the state, by communications and media blackout, claiming that the lockdown was to curb terrorism.
According to Merriam-Webster, the first known use of lockdown occurred in 1973, referring to the confinement of prisoners.
Tracking usage changes through events reported up to 1999 in The New York Times: