I want to mention Selberg's integral, an $n$-dimensional generalization of Euler's beta integral. Selberg published it 1944 in Norwegian in the journal Norsk Matematisk Tidsskrift. Not surprisingly, it did not get a lot of publicity there. Later it was key to results in random matrix theory and other areas. There is an excellent article by Forrester and Warnaar summarizing the history and applications of the integral.