'pro-capitalistically' originates from a combination of the Latin prefix 'pro-' (via Old French) meaning 'for' and the adjective 'capitalistic' (from 'capital' + the adjectival suffix '-istic'), where 'capital' ultimately comes from Latin 'caput' meaning 'head' (extended to 'property, wealth').

'pro-capitalistically' was formed in modern English by adding the adverbial ending '-ally' to 'pro-capitalistic'. The element 'capitalistic' traces back to 19th-century 'capitalist' (derived from 'capital'), which in turn comes from Latin 'caput'.

Initially the components conveyed 'for' ('pro-') plus the sense of 'head' or 'property' (from 'caput'), but the combined term has evolved to mean 'in favor of the capitalist economic system' rather than any literal 'head' meaning.