a small, slow, or irregular quantity of anything coming, going, or proceeding: a trickle of visitors throughout the day.
Origin: 1325–75; Middle English triklen, trekelen (v.), apparently sandhi variant of strikle, perhaps equivalent to strike (in obsolete sense “flow”) + -le
late 14c., possibly an aphetic variant of stricklen "to trickle," a frequentative form of striken "to flow, move" (see strike). The noun is 1580, from the verb. Trickle-down as an adjectival phrase in an economic sense first recorded 1944; the image had been in use at least since Teddy Roosevelt.