Australian Aboriginal avoidance practices

Aboriginal avoidance practices refers to those relationships in traditional Aboriginal society where certain people are required to avoid others in their family or clan. These customs are still active in many parts of Australia, to a greater or lesser extent.
Avoidance relationships are a mark of respect. There are also strong protocols around avoiding, or averting, eye contact, as well as around speaking the name of the dead.
Avoidance of members.
In general, across most language groups, the two most common avoidance relationships are:
Son/daughter-in-law and mother-in-law.
In what is the strongest kinship avoidance rule, some Australian Aboriginal customs ban a person from talking directly to their mother-in-law or even seeing her. A mother-in-law also eats apart from her son-in-law or daughter-in-law and their spouse. If the two are present at the same ceremony, they will sit with their backs to each other but they can still communicate via the wife/husband, who remains the main conduit for communication in this relationship. Often there are language customs surrounding these relationships.
This relationship extends to avoiding all women of the same skin group as the mother-in-law, and, for the mother-in-law, men of the same skin group as the son-in-law. The age of marriage is very different for men and women with girls usually marrying at puberty while a man may not marry until his late 20s or even later. As mothers-in-law and sons-in-law are likely to be of approximately the same age the avoidance practice possibly serves to circumvent potential illicit relationships. It has also been suggested that the custom developed to overcome a common cause of friction in families.
Brother–sister.
This usually takes place after initiation. Prior to this, brothers and sisters play together freely.
Both these avoidance relationships have their grounding in the Australian Aboriginal kinship system, and so are ways of avoiding incest in small bands of closely related people.
There are many other avoidance relationships, including same-sex relationships, but these are the main two.
Sexual relationships.
Once children are older, they are viewed as potential marital partners and their sexual behavior becomes one of strict avoidance until married. Permanent relationships are prescribed by traditional law and often arranged before birth.
Same-sex relationships are viewed in the same light as incest or "wrong" marriages (i.e., to a partner of their own choice or wrong skin group) which carry the same penalties as a domestic crime against the community. However, intimate bodily contact between women regardless of marital status is not considered sexually suggestive but affirmation of friendship and a "right to touch". Touch is particularly important when women tell jokes or discuss matters of a sexual nature. In these circumstances behavior such as "nipple tweaking" and "groin grabbing" are seen as signs of friendship.
Avoidance of naming the dead.
Traditionally, this meant avoiding referring to a deceased individual by name directly after their death as a mark of respect—and also because it is considered too painful for the grieving family. Today the practice continues in many communities, but has also come to encompass avoiding the publication or dissemination of photography or film footage of the deceased as well. Most forms of media include a disclaimer warning Aboriginal and Torres Strait Islanders that the program may contain images and voices of such people who have died (as recommended by the Australian Broadcasting Corporation).
The avoidance period may last anywhere from 12 months to several years. The person can still be referred to in a roundabout way, such as, "that old lady", or by their generic skin name, but not by first name. In some Central Australian communities, if for example, an individual named Alice dies, that name must be avoided in all contexts. This can even include the township Alice Springs being referred to in conversation in a roundabout way. Those of the same name as the deceased are referred to by a substitute name during the avoidance period such as "Kuminjay", used in the Pintubi-Luritja dialect, or "Galyardu", which appears in a mid-western Australia Wajarri dictionary for this purpose. 
This presents some challenges to indigenous people. In traditional society, people lived together in small bands of extended family, and name duplication was less common. Today, as people have moved into larger communities (with upwards of 300 to 600 people), the logistics of name avoidance have become increasingly difficult. Exotic and rare names have therefore become more common, particularly in Central Australia and desert communities, to deal with this new challenge.