means The process of steeping a substance in liquid to extract its flavor, color, or properties, or the resulting liquid itself; also, in medicine, the slow introduction of fluid into the body.

from From Latin infundere, "to pour into" (in-, "in" + fundere, "to pour") — the same fundere that gives us "fountain," "foundry," and "refund." The word arrived in English through Old French in the late Middle Ages, first in the literal sense of pouring liquid in, later settling into the kitchen and the apothecary where the pouring became a patient soaking.