The word 'vexatious' originates from the Latin verb vexare, meaning to shake, agitate, or harass. This Latin term is itself a frequentative form of vehere (to carry), suggesting a sense of being repeatedly jostled or troubled. The past participial stem vexat- was combined with the adjectival suffix -ious, entering Middle English via Anglo-French. The semantic journey thus evolved from the physical act of shaking to the abstract and legal sense of causing persistent mental agitation or harassment.

Structure: vex (to annoy) + at (verb suffix) + ious (adjective suffix) vex: From Latin vexare (to shake, disturb, annoy). The functional role is the core semantic root. at: A Latin verbal suffix forming the past participle stem vexat-. ious: An English adjective-forming suffix, from Latin -iosus, meaning "full of" or "characterized by."