"something taken to whet the appetite," 1820, agent noun from appetize.
Entries linking to appetizer
appetize v.
"make hungry, give an appetite to," 1782 (implied in appetized), irregularly formed (on model of verbs in -ize) from appetite, or else a back-formation from appetizing. The French word is appétissant. "In Fr. only the pples. are found; and in English the simple vb. is perhaps only colloquial" [OED].