Translation: Why are they called shelamim? Because they make peace between the altar, the kohanim, and Israel. The olah is entirely for the fires; the chatas and asham — their fats to the altar and their meat to the kohanim; but the shelamim — blood and emurim to the altar, breast and thigh to the kohanim, and the meat to Israel. Thus it makes peace for all.
In Midrash Tanchuma / Sifra: The name “shelamim” is expounded as creating shared benefit — and therefore peace — among the three parties to the korban.