roof: [OE] The antecedents of roof are far from clear. Its only surviving relative seems to be Dutch roef ‘cabin, coffin lid’, and although it also had links with Old Norse hróf ‘boat-shed’, its ultimate origins remain a mystery.
Old English hrof "roof, ceiling, top, summit; heaven, sky," also figuratively, "highest point of something," from Proto-Germanic *khrofam (cognates: Old Frisian rhoof "roof," Middle Dutch roof, rouf "cover, roof," Dutch roef "deckhouse, cabin, coffin-lid," Middle High German rof "penthouse," Old Norse hrof "boat shed").
No apparent connections outside Germanic. "English alone has retained the word in a general sense, for which the other languages use forms corresponding to OE. þæc thatch" [OED]. Roof of the mouth is from late Old English. Raise the roof "create an uproar" is attested from 1860, originally in U.S. Southern dialect.
