'pet-prohibited' is a compound of 'pet' and 'prohibited'. 'pet' originates from Scots or Middle English 'pet', originally meaning 'tame animal' or 'favored person'. 'prohibited' derives from Latin 'prohibēre', where 'pro-' meant 'forward' and 'habēre' meant 'to hold.'

'pet' appears in Middle English/Scots as 'pet' meaning a tame animal or darling; 'prohibēre' passed into Old French as 'prohiber' and into Middle English as 'prohibiten'/'prohibit', with the past participle forming 'prohibited'; the compound 'pet-prohibited' is a modern English compound formed by combining the noun 'pet' with the past-participle adjective 'prohibited'.

Individually, 'pet' originally meant a tame or favored animal and 'prohibit' originally meant 'to hold off' (from Latin), and together they now form the modern descriptive meaning 'not permitting pets' (i.e., 'pets are forbidden').