'assart' originates from Old French, specifically the word 'essarter' (also attested as 'essartier'), where the element 'es-' (from Latin ex-) meant 'out' and 'sarter/essarter' meant 'to grub up or clear (land)'.

'assart' changed from Old French 'essarter' (and related medieval forms) into Middle English as 'assarten/assart' and eventually became the modern English word 'assart'.

Initially, it meant 'to grub up or clear land (especially woodland)'; over time the word retained this core meaning but became uncommon and is now mainly found in historical or legal contexts referring to the act or the cleared land.