I've always thought the phrase temper tantrum was sort of redundant, because are there really any other kinds of tantrums? The phrase, which was probably adopted so widely due to its memorable alliteration, emerged in the early 1920s, around the time that the word tantrum entered mainstream usage in America. Tantrum had been around in England ever since its first usage in a 1714 letter, when it was spelled tanterum. Other forms like tantarum, tanthrum, tantrim, tantum, and tantell all rose and fell in popularity in the century or so after that, but soon tantrum was predominantly accepted as the correct variant. Despite all that documentation, there is no evidence where tantarum comes from. It looks Latin, but there's nothing connecting it to the language. There is an attestation of it from a 1675 burlesque meaning "penis", but that might not be related. It might also trace to the Tamil word tantiram (meaning "stratagem"), but that too is tenuous. Hopefully, we'll find out someday.
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.