-fold Look up -fold at Dictionary.com
multiplicative word-forming element attached to numerals, from Old English -feald, from Proto-Germanic *-falthaz (cognates: Old Frisiah -fald, Old Norse -faldr, Dutch -voud, German -falt, Gothic falþs), comb. form of *falthan, from PIE *polt-, extended form of root *pel- (3) "to fold" (cognates: Greek -paltos, -plos; Latin -plus; see fold (v.). Native words with it have been crowded out by Latinate double, triple, etc., but it persists in manifold, hundredfold, etc.