The phrase hot dog was first recorded in an 1884 edition of the Evansville, Indiana Daily Courier. The hot part just referred to the temperature, but the dog part had meant "sausage" for several decades before that, probably echoing a suspicion that many sausages were created with dog meat. The moniker became very popular with the youth of the day, and there were several early attestations from college newspapers. It was especially popularized by use in cartoonist Tad Dorgan's popular comic strip in the New York Sun (Dorgan also helped phrases like for crying out loud, the cat's pajamas, and several others reach the mainstream), and was widespread by the 1930s. The use of hot dog! as an exclamation of enthusiasm emerged in 1906 and was made famous through frequent use by Mickey Mouse.
Hello! I'm Adam Aleksic, a sophomore studying government and linguistics at Harvard University, where I co-founded the Harvard Undergraduate Linguistics Society. In addition to etymology, I also really enjoy politics, vexillology, geography, board games, conlanging, and law.