The word 'vanquish' entered English in the 14th century from the Anglo-French venquis-, the past stem of veintre, meaning "to conquer." This, in turn, derives from the Latin verb vincere, which carries the same meaning of defeating or overcoming. The Latin root vincere is traceable to the Proto-Indo-European root weik-, meaning "to fight, to conquer," which also gives us words like 'victory' and 'conviction.' The literal sense of overcoming in battle has been retained in modern English, though its use now extends to metaphorical triumphs in any conflict or competition. The suffix '-ish' was added through the French influence, solidifying its role as a verb describing the act of achieving a decisive conquest.

Structure: vanqu (conquer) + ish (verb suffix) - vanqu: From Latin vincere (to conquer), via Old French vainquir/veintre. The spelling 'vanqu' is the stem form adapted into English. - ish: A verb-forming suffix of Germanic origin, entering English via Old French -iss-, indicating "to make" or "to do".