Old English timber "building, structure," later "building material, trees suitable for building," and "wood in general," from Proto-Germanic *temran (cf. Old Frisian timber "wood, building," Old High German zimbar "timber, wooden dwelling, room," Old Norse timbr "timber," German Zimmer "room"), from PIE *demrom-, from root *dem-/*dom- "build" (source of Greek domos, Latin domus; see domestic (adj.)).
The related Old English verb timbran, timbrian was the chief word for "to build" (cf. Dutch timmeren, German zimmern). As a call of warning when a cut tree is about to fall, it is attested from 1912 in Canadian English. Timbers in the nautical slang sense (see shiver (n.)) is from the specialized meaning "pieces of wood composing the frames of a ship's hull" (1748).