'vomit-preventing' is a modern English compound combining the noun/verb 'vomit' and the present-participle form of 'prevent' ('preventing'), formed within modern English word-formation practices.

'vomit' ultimately comes from Latin 'vomere'/'vomitus' (to vomit) via Old French and Middle English, while 'prevent' comes from Latin 'praevenīre' (to come before) through Old French 'prevenir' into Middle English; the compound itself is a straightforward modern English formation joining the two words with a hyphen.

The components 'vomit' and 'prevent' retained their core senses (to expel stomach contents; to stop/hinder). In the compound, the combined meaning became the descriptive sense 'stopping vomiting'.