in early use also engredient, early 15c., "something forming part of a mixture," from Latin ingredientem (nominative ingrediens) "that which enters into" (a compound, recipe, etc.), present participle of ingredi "go in, enter," from in- "in" (from PIE root *en "in") + gradi "to step, go" (from PIE root *ghredh- "to walk, go"). Also from early 15c. as an adjective, "forming part of a mixture."
Proto-Indo-European root meaning "to walk, go."
It forms all or part of: aggress; aggression; aggressive; centigrade; congress; degrade; degree; degression; digress; digression; egress; gradation; grade; gradual; graduate; grallatorial; gravigrade; ingredient; ingress; plantigrade; progress; progression; regress; regression; retrograde; retrogress; tardigrade; transgress; transgression.
It is the hypothetical source of/evidence for its existence is provided by: Latin gradus "a step, a pace, gait," figuratively "a step toward something, a degree of something rising by stages;" gradi "to walk, step, go;" Lithuanian gridiju, gridyti "to go, wander;" Old Church Slavonic gredo "to come;" Old Irish in-greinn "he pursues."
toffee-like confection, 1802, from butter (n.), which is a main ingredient; the second element uncertain; perhaps from its having been made in Scotland.
"thick, whitish fluid containing spermatozoa as its essential ingredient," late 14c., from Latin semen "seed of plants, animals, or men; race, inborn characteristic; posterity, progeny, offspring," figuratively "origin, essence, principle, cause" (from PIE *semen- "seed," suffixed form of root *sē- "to sow").
c. 1600, "to fill with an ingredient, spirit, etc.;" 1640s as "make (a female) pregnant," from Late Latin impraegnatus "pregnant," past participle of impraegnare "to render pregnant," from assimilated form of in- "into, in" (from PIE root *en "in") + praegnare "make pregnant" (see pregnant). Earlier in same sense was impregn (1530s), which OED marks as "now only in poetic use."