'embitter' originates from Middle English, specifically the word 'embittren,' where 'em-' meant 'to make' and 'bitter' meant 'having a sharp taste or feeling.'

'embittren' transformed into the modern English word 'embitter' through the influence of Old English and Middle English.

Initially, it meant 'to make bitter in taste,' but over time it evolved into its current meaning of 'to make someone feel bitter or resentful.'