'decorative-only' is a compound of 'decorative' and 'only.' 'decorative' originates from Latin, specifically the word 'decorativus' (from 'decōrāre'), where the root 'decōr-' meant 'beauty' or 'to adorn'; 'only' originates from Old English, specifically the word 'ān', where 'ān' meant 'one' or 'alone'.

'decorative' changed from Latin 'decorativus' through Old French/French forms (e.g. 'décoratif') and Middle English into modern English 'decorative.' 'only' evolved from Old English 'ān' to Middle English 'onli' and then to modern 'only.' The hyphenated compound 'decorative-only' is a relatively modern English formation used for emphasis.

Initially, 'decorative' carried the sense 'to adorn' and 'only' meant 'one' or 'alone'; over time 'decorative' became the adjective 'ornamental' and, combined with 'only,' the compound came to mean 'solely ornamental, not functional.'