means The statistical measure of how far a set of values spreads out from their mean, calculated as the average of the squared differences from that mean — and, more loosely, any difference or disagreement between things.

from From Latin 'variantia,' meaning difference or diversity, built on the verb 'variare,' to change or diversify, which itself comes from 'varius' — varied, mottled, speckled. The word arrived in English through Old French 'variance' in the medieval period, long carrying the everyday sense of disagreement or discrepancy (as in 'at variance with'). The precise statistical meaning is a much later graft: it was coined in the early 20th century by the statistician Ronald Fisher, who borrowed the ordinary word and pinned a hard mathematical definition onto it.