Fridge is short for refrigerator, that giant kitchen appliance that keeps food cold. If you’re too hungry to say five syllables, just say you’re going to see what’s in the fridge.
Although fridge is a little word, a fridge can be anything from a regular-sized refrigerator to one of those little mini-fridges that live in a dorm room or man cave. Fridge sounds like frigid, which means very cold. The colloquial fridge has been around since the mid-1920s, possibly inspired by the well-known refrigerator brand Frigidaire.