late Old English byldan "construct a house," verb form of bold "house," from Proto-Germanic *buthlam (cf. Old Saxon bodl, Old Frisian bodel "building, house"), from PIE *bhu- "to dwell," from root *bheue- "to be, exist, grow" (see be). Rare in Old English; in Middle English it won out over more common Old English timbran (see timber). Modern spelling is unexplained. Figurative use from mid-15c. Of physical things other than buildings from late 16c. Related: Builded (archaic); built; building.