Gizzard is a word referring to the stomachs of birds, and it has meant the same thing since Latin. In Middle English, it could also be spelled geser or gyser, and in Old French, the term was attested as taking the forms gisier, giser, geser, and several more. In Latin, it was gicerium, which shifted away from the original noun gigeria, meaning "cooked insides of a bird". Note that over time, the word grew both more specific (from "insides" in general to "stomach"), and broader (from "cooked" to not necessarily heated up in any particular manner). I think that's pretty interesting, but it gets even better, with a mysterious turn! The origin of gigeria is unknown, but there are some theories. One exotic idea is that it could be from Middle Persian, because of a Persian cognate; another is that it is from a Proto-Indo-European sounding like hyekwr and meaning "liver". Nobody knows for sure, but it certainly is fascinating speculation!
Adam Aleksic, a rising sophomore studying linguistics and government at Harvard University, has been described as the internet's sixth most famous etymologist. He also has disturbing interests in politics, vexillology, geography, board games, conlanging, and law.