Etymology
1. From Middle English knobbe, from Middle Low German knobbe (“knob, knot in wood, bud”), probably ultimately from a variant of Proto-Germanic *knappô (“knob, lump”), one of several kn- words related to *knudaną (“to knead”).
2. Compare Middle Dutch knobbe, cnoppe, Middle Low German knobbe (“knob, knot in wood”), knubbe, Dutch knop (“knob, button, bud”), Old Frisian knopp, knapp, Old High German knopf (“bud, pommel of a sword, knot, loop”), Middle High German knospe, German Knopf (“button, knob”), Knospe (“bud”), Danish knap (“button”), knop (“knob, button, bud”), Faroese knappur (“button”), Icelandic hnappur (“button”), Norn knapp (“round button”), knubbi (“potato”), snapp (“knob, round top”), Norwegian and Swedish knapp (“button”), Norwegian knopp (“bud”), Swedish knopp (“bud, knob”), Finnish nappi (“button, knob”), nuppi (“knob, pommel”), Old Norse knyfill (“short horn”).
3. Also compare Middle English knap, knappe (“small projection, knob (button, tassel, tuft, etc.), hill, hilltop, etc.)”), from Old English cnæp, cnæpp (“summit, top”), which is possibly related to Old Norse knappr (“small projection, knob (button, head of a stick, etc.)”) (whence English knop), from Proto-Germanic *knappô (“knob, lump”), *knuppô (“lump, clod”).
4. Cognate with Dutch knob, knobbel (“knob”), German Knubbe, Knubbel (“knob”). See also knop. For the sense of a rounded hill, see nab and knab. See: English '
knop'.