Around the beginning of what two things did word universitas start to become prevalent?
The original Latin word "universitas" refers in general to "a number of persons associated into one body, a society, company, community, guild, corporation, etc." At the time of the emergence of urban town life and medieval guilds, specialised "associations of students and teachers with collective legal rights usually guaranteed by charters issued by princes, prelates, or the towns in which they were located" came to be denominated by this general term. Like other guilds, they were self-regulating and determined the qualifications of their members.
Just as artist and inventor Leonardo da Vinci – partaking of the zeitgeist though not himself a humanist – advocated study of human anatomy, nature, and weather to enrich Renaissance works of art, so Spanish-born humanist Juan Luis Vives (c. 1493–1540) advocated observation, craft, and practical techniques to improve the formal teaching of Aristotelian philosophy at the universities, helping to free them from the grip of Medieval Scholasticism. Thus, the stage was set for the adoption of an approach to natural philosophy, based on empirical observations and experimentation of the physical universe, making possible the advent of the age of scientific inquiry that followed the Renaissance.