peptide (n.)

a general name for a substance into which the nitrogenous elements of food are converted by digestion, 1860, from German Pepton (1849), from Greek pepton, neuter of peptos "cooked, digested," verbal adjective of peptein "to cook" (from PIE root *pekw- "to cook, ripen"). Related: Peptonic.

Proto-Indo-European root meaning "to cook, ripen." 

It forms all or part of: apricot; biscuit; charcuterie; concoct; concoction; cook; cuisine; culinary; decoct; decoction; drupe; dyspepsia; dyspeptic; eupeptic; kiln; kitchen; peptic; peptide; peptone; precocious; pumpkin; ricotta; terra-cotta.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit pakvah "cooked, ripe;" Avestan -paka- "cooked;" Greek peptein "to cook, ripen, digest," pepon "ripe;" Latin coquere "to cook, prepare food, ripen, digest, turn over in the mind," Oscan popina "kitchen;" Lithuanian kepti "to bake, roast;" Old Church Slavonic pecenu "roasted;" Welsh poeth "cooked, baked, hot."

peptide built from a large number of amino acids, 1903, from German polypeptid; see poly- + peptide.