Old English feowerfeald; see four + -fold. As an adverb from 1530s. Similar formation in Old Frisian fiuwerfald, Dutch viervoudig, Old High German fiervalt, German vierfältig, Danish firfold, Gothic fidurfalþs.
fourchette
four-corners
four-door
four-eyes
four-flusher
fourfold
four-footed
Fourierism
four-poster
fourscore
foursome
