The modern refrigerator was invented in 1834, but the word for something that cools has been around since the 1610s. This noun form comes from the verb refrigerate, which has existed since the 1530s. Refrigerate derives from Latin refrigerare, which is composed of the prefix re- and the root frigerare, or "cool". Therefore, refrigerare means "to cool again". The etymon of frigerare is frigus, meaning "cold" in general, which in turn comes through Proto-Italic from the Proto-Indo-European reconstruction srig, with the same definition. Now, why does the common nickname for the refrigerator, fridge, have a d in it? Simply to reinforce the natural sounds of the cropping, which in itself is a pretty unexpected formation. The most interesting part of this all is the name of the fridge company Frigidaire (registered as a brand name in the US but in some international cases used as ubiquitously as Kleenex for tissue). It's a play on words messing around by combining the terms fridge, refrigerator, and frigid air, quite an interesting amalgamation.
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.