acidulent comes from Latin acidulus ('slightly sour'), diminutive of acidus ('sour'), from acēre ('to be sour'), from Proto-Indo-European *h2eḱ- ('sharp'). The path is chiefly one of transmission: an older form is taken into English, with the word's shape and meaning carried through the language names and forms preserved in the history. In modern use, the adjective sense is "somewhat sour or sharp in taste or temper", which keeps the etymology connected to the word's present dictionary value rather than treating it as a merely historical label. The wider word family includes related English forms such as acid, acidulous, acidify, showing how the same base continues to support neighboring English vocabulary. The principal historical forms in the chain include Latin acidulus, Proto-Indo-European *h₂eḱ-, which anchor the explanation in named linguistic material.