"hand-held cutting instrument consisting of a short blade and handle," late Old English cnif, probably from Old Norse knifr "knife, dirk," from Proto-Germanic *knibaz (source also of Middle Low German knif, Middle Dutch cnijf, German kneif), a word of uncertain origin. To further confuse the etymology, there also are forms in -p-, such as Dutch knijp, German kneip. French canif "penknife" (mid-15c.) is probably of Germanic origin, perhaps from Frankish. For pronunciation, see kn-.
1865, "stab or kill with a knife," from knife (n.). Intransitive meaning "move as a knife does" is from 1920. Related: Knifed; knifing.