late Old English cnif, probably from Old Norse knifr, from Proto-Germanic *knibaz (cf. Middle Low German knif, Middle Dutch cnijf, German kneif), of uncertain origin. To further confuse the etymology, there also are forms in -p-, e.g. Dutch knijp, German kneip. French canif "penknife" (mid-15c.) is borrowed from Middle English or Norse.
1865, from knife (n.). Related: Knifed; knifing.