The International Thespian Society takes its name from the Greek poet, playwright, and chorus leader Thespis, who is considered to be the first actor. Before Thespis, who lived in the sixth century BCE, Greek theatre was performed entirely by a chorus. Tradition has it that Thespis was the first performer to step away from the chorus and deliver lines to them, introducing the concept of dialogue. He is also credited with inventing the theatrical mask.

“It is generally supposed that Thespis, who managed a traveling company, transported his actors in wagons, which also served as their stage,” according to The Cassell Companion to Theatre, which quotes this couplet from John Dryden:
Thespis, the first professor of our art, At country wakes sang ballads from a cart.