foist v.

Old English fyst "fist, clenched hand," from West Germanic *fusti- (source also of Old Saxon fust, Old High German fust, Old Frisian fest, Middle Dutch vuust, Dutch vuist, German Faust), from Proto-Germanic *funhstiz, probably ultimately from a PIE "hand" word that is ultimately cognate with the root *penkwe- "five" (compare Old Church Slavonic pesti, Russian piasti "fist"), in reference to the five fingers.

Meaning "a blow with the fist" is from 1767. Fist-fight "duel with the fists" is from c. 1600. As a verb, Old English had fystlian "to strike with the fist."

Proto-Indo-European root meaning "five."

It forms all or part of: cinquain; cinque; cinquecento; cinquefoil; fifteen; fifth; fifty; fin (n.) "five-dollar bill;" finger; fist; five; foist; keno; parcheesi; penta-; pentacle; pentad; Pentateuch; Pentecost; pentagon; pentagram; pentameter; pentathlon; Pentothal; Pompeii; Punjab; punch (n.2) "type of mixed drink;" quinary; quincunx; quinella; quinque-; quinquennial; quint; quintain; quintet; quintile; quintessence; quintillion; quintuple.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit panca, Greek pente, Latin quinque, Old Church Slavonic pęti, Lithuanian penki, Old Welsh pimp, Old English fif, Dutch vijf, Old High German funf.