'lactation-suppressing' is a Modern English compound formed from 'lactation' + 'suppressing'. 'lactation' ultimately originates from Latin 'lactatio' (from 'lac'/'lact-') where 'lac' meant 'milk'; 'suppressing' derives from Latin 'suppressus', the past participle of 'supprimere', where 'sub-'/ 'sup-' meant 'under' and 'premere' meant 'to press'.

'lactation' entered English via New Latin/medical Latin (Latin 'lactatio'), while 'suppress' passed into English via Old French (e.g. 'supprimer') from Latin 'supprimere'; the compound form 'lactation-suppressing' is a descriptive Modern English formation used in medical contexts.

Individually, 'lactation' originally referred to the act or process of producing milk and 'suppress' meant to press down or restrain; combined as a compound, the term evolved to specifically describe agents or actions that stop or reduce milk production.