'unpriceable' originates from English, formed from the negative prefix 'un-' + 'price' + the suffix '-able', where 'un-' meant 'not', 'price' (from Old French 'pris', from Latin 'pretium') meant 'price' or 'value', and '-able' meant 'capable of' or 'able to be'.

'price' came from Latin 'pretium' which passed into Old French as 'pris' and into Middle English as 'prise/price', eventually becoming the modern English 'price'. The negative prefix 'un-' is Old English in origin and the adjectival suffix '-able' comes via Old French/Latin (from Latin '-abilis'). These elements combined in modern English to form 'unpriceable'.

Initially the components referred literally to 'not able to be priced' (not able to assign a monetary value); over time the word has maintained that literal sense but is also commonly used figuratively to mean 'extremely valuable' or 'priceless'.