Past tense of cavalier used as a verb; to treat someone dismissively or in a high-handed manner, or to act as a cavalier.
From the noun/adjective 'cavalier' with the past tense suffix '-ed.' The verb form emerges from the adjective's meaning of 'dismissive or casual' (in the sense of the historical Cavalier attitude). This shows how English allows easy conversion between parts of speech.
To 'cavalier' someone (meaning to dismiss them rudely) comes from the historical Cavaliers' reputation for arrogance and cavalier attitudes—their very name became a verb describing the attitude they embodied. It's a word that carries historical baggage in its grammar.
Complete word intelligence in one call. Free tier — 50 lookups/day.