"support," mid-15c., from Middle Dutch proppe "vine prop, support," of unknown origin. Probably related to Old High German pfropfo, German pfropfen "to prop," perhaps from Latin propago "a set, layer of a plant" (see propagation). Irish propa, Gaelic prop are from English.
"object used in a play," 1898, from props (1841), shortened form of properties (which was in theatrical use from early 15c.). Props as slang shortening for proper respects (or something similar) appeared c. 1999.
"to support," mid-15c., probably from prop (n.1) or a related verb in Dutch. Related: Propped; propping.
short for propeller, 1914.