joist: [14] Etymologically, a joist is a wooden beam on which boards ‘lie’ down. The word’s ultimate ancestor is the Latin verb jacēre ‘lie down’ (from which English also gets adjacent). Its neuter past participle jacitum was taken into Old French as a noun, giste, which denoted a ‘beam supporting a bridge’ (its modern French descendant, gîte ‘home’ – that is, ‘place where one lies down’ – is currently infiltrating English). Middle English took over the Old French word, which from the 15th century gradually began to change to joist. => adjacent[joist etymology, joist origin, 英语词源]