The verb 'vomit' entered English in the late 14th century from the Anglo-French 'vomiter', which derived from Latin 'vomitare', a frequentative form of 'vomere', meaning 'to spew forth, disgorge'. This Latin root can be traced back to the Proto-Indo-European (PIE) stem wemh-, meaning 'to spew, vomit', which also gave rise to words like the Greek 'emein' (to vomit). The core concept has remained remarkably stable from its ancient PIE expression of forceful expulsion to its modern medical and general usage describing the involuntary reflex of ejecting stomach contents.

The word 'vomiting' is the present participle/gerund form of the verb 'vomit'. It is treated as a simplex unit for morpheme analysis as segmenting it further ('vomit' + 'ing') separates the core word from its grammatical suffix, which does not aid in understanding the core meaning's origin.