'self-denyingly' originates from modern English compounding of 'self-' and the present participle 'denying' (from 'deny'), where 'self-' meant 'oneself' and 'deny' is the verb 'to refuse or withhold'.

'deny' originates from Latin 'denegare' via Old French (e.g. 'deneier'/'denier') and Middle English ('denyen'/'denyen'), which produced the modern English verb 'deny'; 'self-' has been used in English as a reflexive/intensifying prefix since Old English and later, forming compounds like 'self-denying' that then take the adverbial suffix '-ly' to produce 'self-denyingly'.

Initially, 'deny' meant 'to refuse or say no to'; combining it with 'self-' produced the notion 'to refuse oneself (something)'; over time 'self-denying' came to mean 'willingly foregoing personal pleasures', and 'self-denyingly' now means 'in that manner'.