'untoasted' originates from English, formed by the negative prefix 'un-' + the past participle 'toasted' (from the verb 'toast'), where 'un-' meant 'not' and 'toast' ultimately traces to Latin 'tostare' meaning 'to roast or scorch.'

'toast' comes from Latin 'tostare' (to roast/scorch), entered English via medieval/Old French and Middle English (e.g. Middle English 'tosten'), becoming modern English 'toast'; 'untoasted' is a later English formation using the prefix 'un-' attached to the past participle.

Initially, 'toast' meant 'to roast or scorch'; over time it narrowed to mean 'to brown bread by heat,' and 'untoasted' accordingly came to mean 'not toasted' (not browned by heat).