late 14c. (implied in forestalling), "to lie in wait for;" also "to intercept goods before they reach public markets and buy them privately," which formerly was a crime (mid-14c. in this sense in Anglo-French), from Old English noun foresteall "intervention, hindrance (of justice); an ambush, a waylaying," literally "a standing before (someone)," from fore- "before" + steall "standing position" (see stall (n.1)). Modern sense of "to anticipate and delay" is from 1580s. Related: Forestalled; forestalling.
updated on December 19, 2014