'full-form' is an English compound formed from 'full' + 'form'; 'full' comes from Old English 'ful' meaning 'full, abundant', and 'form' comes from Latin 'forma' meaning 'shape' or 'appearance'.

'full' developed from Old English 'ful' and 'form' entered English via Latin 'forma' through Old French 'forme' into Middle English; the compound phrase 'full form' has been used in Modern English to mean the complete version and is sometimes hyphenated as 'full-form'.

Initially the elements meant 'complete/abundant' (full) and 'shape/arrangement' (form); over time the compound evolved to mean 'the complete (unabbreviated) version' of a word or term.