"base frame of an automobile," 1903, American English; earlier "window frame" (1660s), from French châssis "frame," Old French chassiz (13c.) "frame, framework, setting," from chasse "case, box, eye socket, snail's shell, setting (of a jewel)," from Latin capsa "box, case;" see case, n.2 + French -is, collective suffix for a number of parts taken together. Compare sash, n.2.