'covertly-expressed' originates from a combination of 'covertly' and 'expressed': 'covertly' ultimately from Latin 'cooperire' ('to cover'), via Old French 'covrir' and Middle English 'covert'; 'expressed' from Latin 'exprimere,' where 'ex-' meant 'out' and 'primere' meant 'to press'.

'covertly-expressed' combined Middle English 'covert' (from Old French 'covrir') + English suffix '-ly' with Middle English 'express(e)' (from Old French 'exprimer'); this pairing eventually became the modern English compound adjective 'covertly-expressed'.

Initially, it drew on 'covered/hidden' and 'pressed out/expressed', but over time it settled into the sense of 'not stated openly but communicated indirectly'.