'toothache-relieving' originates from Modern English, specifically the compound of 'toothache' and the present participle 'relieving' (from 'relieve'). 'Toothache' itself is formed from 'tooth' + 'ache'; 'tooth' comes from Old English 'toþ' and 'ache' from Old English 'æce'. 'Relieve' ultimately comes from Latin 'levare' via Old French.

'toothache' changed from Old English elements 'toþ' (tooth) + 'æce' (ache) and eventually became the Modern English 'toothache'. 'Relieve' entered English via Old French (e.g. 'relever') from Latin 'levare', and its present participle 'relieving' follows regular Modern English participle formation, producing the compound adjective 'toothache-relieving'.

Initially, the components meant 'pain in a tooth' ('toothache') and 'to lift/lighten' (from Latin 'levare' > 'relieve'); over time these combined to describe something that 'lessens or eases tooth pain', the current meaning.