luncheon

Of uncertain origin. Possibly derived from an earlier *lumpchin, *lumpchen, a diminutive of lump (“chunk, parcel of food, lunch”), thus related to lunch. It is unclear which came first: whether lunch is a shortening of luncheon, or whether luncheon is an augmentation of lunch. Possibly also a dissimilatory form of or influenced by nuncheon (“light snack taken in the afternoon”).

Noun sense 2 (“sausage”) is likely a ellipsis of luncheon sausage or luncheon meat.