Q From Elisabeth Okasha in Ireland: Yesterday a student asked me the etymology of the word slang, suggesting it might be derived from two words, the second being language. I admitted that I had no idea of the word’s history but said I would look it up for her. However my Shorter Oxford (new edition) admits ignorance too.
A That’s true of all the sources I’ve consulted, as well. Nobody seems to know where the word comes from (though everyone is sure it is not a compound of any word with language). It appeared in the eighteenth century, itself as what we would now call a slang term, with various meanings, of which our modern sense is the only one that has survived. Some have tried to trace it back to a Norwegian form sleng-, implying offensive language (found only in compounds) but others deny that connection on the grounds that the dates don’t support a link. There is a modern facetious formation slanguage, but that’s an obvious blend of slang and language.