Etymology

ca. 1425–75; Middle English to make a sound with right forefinger and thumb; uncert. orig.

a fillip gradually became “something of small importance; a trifle.” “The rest is not worth a fillip with the finger.” And, the word could also express a short space of time (perhaps the time it took to “flick” the finger). “The tortoise..in a fillip of the finger was down in the gardens of Riu Gu.” Only in the 18th and 19th centuries did its current usage, as encouragement or stimulus, tend to dominate.

Noun

1. A flick; the act of releasing the index finger from the hold of a thumb with a snap.
2. Something that excites or stimulates.

   This measure gave a fillip to the housing market.

   This athlete's victory provided a much-needed fillip for national pride.