In Italy's New Year's Eve tradition, lentils symbolize money and prosperity.
Lentils are often served at the turn of the year because their small, round, coin-like shape suggests wealth. A common celebratory meal pairs them with cotechino, a seasoned pork sausage, or zampone, a stuffed pig's trotter. The meal expresses a wish for abundance in the coming year.
The symbolism is cultural rather than nutritional or scientific. Lentils are also valued as an inexpensive, protein-rich food, but their New Year role comes from their appearance and longstanding custom. Families may serve them shortly after midnight or as part of the New Year's Day meal.
The tradition is sometimes described as an Italian Christmas custom because the foods can appear during the broader winter holiday period. For the specific New Year's prosperity association, however, lentils are the characteristic answer. Cotechino and zampone are accompanying foods, not the legume itself.