An Etymological Dictionary of Astronomy and Astrophysics

Prefix denoting five, fivefold (e.g. pentacyclic, pentahedron, pentahydrate).

Etymology (EN): From Gk. pent-, penta-, combining forms from pente “five;” cognate with Pers. panj, E. five, as below.

Etymology (PE): Panj, from Mid.Pers. panj, Av. panca; cf.
Skt. pánca; Gk. pente; L. quinque; O.E. fif, from P.Gmc. *fimfe (O.S. fif, O.H.G. funf);
from PIE base *penk^we “five.”