'lawfully-endorsed' originates from English elements: 'lawfully' (from Old English 'lagu' via 'law' + suffixes '-ful' and '-ly') and 'endorsed' (from Medieval Latin 'indorsare', where 'in-' meant 'on' and 'dorsum' meant 'back').

'indorsare' transformed through Old/Middle French 'endosser/endosser' into English 'endorse', whose past participle 'endorsed' combined with the adverb 'lawfully' to form the modern compound modifier 'lawfully-endorsed'.

Initially, 'endorse' referred to writing on the back of a document; over time it broadened to mean 'approve or support', so 'lawfully-endorsed' now conveys approval that is legally valid.