mid-14c., replenishen, "provide" with food or drink, also riches, beauty, etc., from Old French repleniss-, extended present-participle stem of replenir "to fill up," from re-, here perhaps an intensive prefix based on the notion of "fill repeatedly," thus "fill completely" (see re-), + -plenir, from Latin plenus "full" (from PIE root *pele- (1) "to fill").
Specifically as "to fill up again, restore to a former amount or condition" by 1610s. Related: Replenished; replenishing; replenishment.
It forms all or part of: accomplish; complete; compliment; comply; depletion; expletive; fele; fill; folk; full (adj.); gefilte fish; hoi polloi; implement; manipulation; nonplus; plebe; plebeian; plebiscite; pleiotropy; Pleistocene; plenary; plenitude; plenty; plenum; plenipotentiary; pleo-; pleonasm; plethora; Pliocene; pluperfect; plural; pluri-; plus; Pollux; poly-; polyamorous; polyandrous; polyclinic; polydactyl; polydipsia; Polydorus; polyethylene; polyglot; polygon; polygraph; polygyny; polyhedron; polyhistor; polymath; polymer; polymorphous; Polynesia; polyp; Polyphemus; polyphony; polysemy; polysyllabic; polytheism; replenish; replete; supply; surplus; volkslied.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit purvi "much," prayah "mostly;" Avestan perena-, Old Persian paru "much;" Greek polys "much, many," plethos "people, multitude, great number," ploutos "wealth;" Latin plus "more," plenus "full;" Lithuanian pilus "full, abundant;" Old Church Slavonic plunu; Gothic filu "much," Old Norse fjöl-, Old English fela, feola "much, many;" Old English folgian; Old Irish lan, Welsh llawn "full;" Old Irish il, Welsh elu "much."
"to fund again or anew, replenish a (public) fund or debt," 1860, from re- + fund (v.). With hyphenated spelling and full pronunciation of the prefix to distinguish it from refund. Related: Re-funded; re-funding.
late 14c., reneuen, "make (something) like new, refurbish; begin (an activity) again; replenish, replace with a fresh supply; restore (a living thing) to a vigorous or flourishing state," also figurative, of spiritual states, souls, etc.; from re- "again" + Middle English newen, neuen "resume, revive, renew" (see new). A Latin-Germanic hybrid formed on analogy of Latin renovare. From early 15c. as "be restored, flourish once more." Related: Renewed; renewing.
Old English fyllan "to fill, make full, fill up, replenish, satisfy; complete, fulfill," from Proto-Germanic *fulljanan "to fill" (source also of Old Saxon fulljan, Old Norse fylla, Old Frisian fella, Dutch vullen, German füllen, Gothic fulljan "to fill, make full"), a derivative of adjective *fullaz "full" (see full (adj.)). Related: Filled.
To fill the bill (1882) originally was U.S. theatrical slang, in reference to a star of such magnitude his or her name would be the only one on a show's poster. To fill out "write in required matter" is recorded from 1880.