1530s, "to digest" (a sense now obsolete), from Latin concoctus, past participle of concoquere "to digest; to boil together, prepare; to consider well," from assimilated form of com "together" (see con-) + coquere "to cook, prepare food, ripen, digest," from PIE root *pekw- "to cook, ripen."
Meaning "to prepare an edible thing, combine and prepare the elements of" is from 1670s, metaphorically extended beyond cooking to "devise, plan" by 1792. Related: Concocted; concocting.
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."
c. 1500, "to find, discover" (obsolete), a back-formation from invention or else from Latin inventus, past participle of invenire "to come upon; devise, discover."
The general sense of "make up, fabricate, concoct, devise" (a plot, excuse, etc.) is from 1530s, as is that of "produce by original thought, find out by original study or contrivance." Related: Invented; inventing.