'fatwood' originates from English, specifically the compound 'fat' + 'wood', where 'fat' ultimately comes from Old English 'fætt' meaning 'fat' (here used of oily/resinous substance) and 'wood' comes from Old English 'wudu' meaning 'wood'.

'fatwood' developed in modern English as a compound of 'fat' + 'wood' (formed from Old English elements); the term became common in North American usage in the 18th–19th centuries to name resin-rich pine knots used as kindling.

Initially it literally meant 'fat (i.e. resin)-containing wood'; over time it became a fixed term specifically for resin-saturated pine knots used as firestarters.