Meaning

verb twist into a state of deformity

verb make complaining remarks or noises under one's breath

adjective used of old persons or old trees; covered with knobs or knots

originFirst attested Shakespeare 1603: : Thy sharpe and sulpherous bolt Splits the vn-wedgable [unwedgable] and gnarled Oke [oak]. : Measure for Measure, Act II, scene ii, line 116 Variant of knurled, from knurl. By surface analysis, gnarl + -ed, though gnarl is a later back-formation. Popular use by 19th century.

Etymology from Wiktionary, CC BY-SA 3.0