late 14c., knobe, probably from a Scandinavian or German source (compare Middle Low German knobbe "knob," Middle Dutch cnoppe, Dutch knop, Old Frisian knopp, knapp, Old High German knopf, German Knopf "button," Old Norse knyfill "short horn"). Meaning "knoll, isolated round hill" is first recorded 1640s, especially in U.S. For pronunciation, see kn-.
adjective suffix, "full of or characterized by," from Old English -ig, from Proto-Germanic *-iga- (source also of Dutch, Danish, German -ig, Gothic -egs), from PIE -(i)ko-, adjectival suffix, cognate with elements in Greek -ikos, Latin -icus (see -ic). Originally added to nouns in Old English; used from 13c. with verbs, and by 15c. even with other adjectives (for example crispy).
<a href="https://www.etymonline.com/word/knobby">Etymology of knobby by etymonline</a>
Harper, D. (n.d.). Etymology of knobby. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/knobby