Yours, Etc.: Origins and Uses of 8 Sign-Offs
late 14c., "open air place in ancient times for viewing spectacles," from Old French theatre (12c.), from Latin theatrum, from Greek theatron "theater," literally "place for viewing," from theasthai "to behold" (cf. thea "a view," theates "spectator") + -tron, suffix denoting place. Meaning "building where plays are shown" (1570s) was transferred to that of "plays, writing, production, the stage" (1660s). Spelling with -re prevailed in Britain after c.1700, but American English retained or revived the older spelling in -er. Generic sense of "place of action" is from 1580s; especially "region where war is being fought" (1914).
The Theatre of the Absurd strives to express its sense of the senselessness of the human condition and the inadequacy of the rational approach by the open abandonment of rational devices and discursive thought. [M. Esslin, "Theatre of the Absurd," 1961]