knurl (n.) Look up knurl at Dictionary.com
"hard excrescence," c. 1600, probably a diminutive of Middle English knor "knot" (c. 1400), related to gnarled, from Proto-Germanic *knur- (source also of German knorren "a knotty excrescence," Dutch knor "knob," Swedish dialectal knurr "hard swelling"). Related: Knurly.