'bile-reducing' is a modern English compound formed from 'bile' and the verb 'reduce'. 'Bile' ultimately comes via Old English from Latin 'bilis'. 'Reduce' originates from Latin 'reducere', where 're-' meant 'back' and 'ducere' meant 'to lead'.

'reduce' developed from Latin 'reducere' to Old French 'reduire' and Middle English 'reducent/reduken' before becoming modern English 'reduce'. 'bile' is from Old English and Latin 'bilis', and the compound 'bile-reducing' is a straightforward modern English formation combining those elements.

Originally 'reduce' had senses related to 'lead back' in Latin, but its meaning shifted to 'bring down' or 'make smaller'; in this compound it specifically denotes 'causing a reduction in bile'.