Webster's Revised Unabridged Dictionary · 1913

Gnarl

Gnarl , intransitive verb

[From older gnar, prob. of imitative origin; compare German knarren, knurren. Dutch knorren, Swedish knorra, Danish knurre.]

To growl; to snarl.
And wolves are gnarling who shall gnaw thee first. — Shakespeare

Gnarl , noun

[See Gnar, n.]

a knot in wood; a large or hard knot, or a protuberance with twisted grain, on a tree.