'breakfast-related' is a modern compound formed from 'breakfast' + the adjective-forming element 'related' (from 'relate' + '-ed'). 'Breakfast' is from Old English 'brēk' + 'fæstan' where the sense was 'to break a fast.' 'Related' comes from Latin 'relatus' (past participle of 'referre') via Old French/Medieval Latin and English 'relate'.

'breakfast' originated in Old English as a compound meaning 'to break the fast' and survived into Modern English as 'breakfast'. 'Related' developed from Latin 'relatus' through Old French/Medieval Latin into Middle English 'relaten/relate' and the adjectival/past participle form 'related'. These elements combined in Modern English to form the descriptive compound 'breakfast-related'.

Initially, 'breakfast' literally meant 'the breaking of a fast' and has remained close to that meaning, now referring to the morning meal; 'related' originally meant 'brought back' or 'referred' (from Latin) and shifted to mean 'connected'—together now mean 'connected to breakfast'.