means To make something smaller, fewer, or less in size, amount, degree, or intensity — or, in cooking, to thicken a liquid by simmering off its water.

from From Latin reducere, literally "to lead back" — from re- ("back") plus ducere ("to lead," the same root that gives us conduct, induce, and duke). Early English uses leaned on that literal sense of leading or bringing something back to an earlier state; the modern meaning of "making less" grew out of the idea of bringing a thing down or back to a smaller measure. The kitchen sense, that patient simmering-down of a sauce, is the same logic worn into an apron.