'gnarl' originates from Middle English, specifically the word 'gnar(l)e', where the root meant 'knot' or 'protuberance'.

'gnarl' developed from Middle English 'gnar(le)' and earlier Germanic roots related to words for knots or burls, eventually becoming the modern English 'gnarl'.

Initially it meant 'a knot or protuberance in wood', and over time the sense expanded to include any twisted, knotted mass and the verb sense 'to make knotted' or 'to become knotted'; the core idea of a twisted lump has largely remained.