Some words sprout slang synonyms because they’re naughty enough to advert to indirectly or in code; others sprout them just because they’re unpleasant. Say, for instance, an exceptionally undesirable result on a test, or a profound lack of financial return on an investment or effort. You may want to express your disappointment in a glancing way, one that has a certain style, a certain vehemence even, but that attenuates the sting just slightly by not naming the thing exactly.
So you stand there, looking at your test paper or your financial statements or your empty hand, saying “Shoot. Fuddle-duddle. Son of a bungee jumper. Goshdarn it all to heck.” And someone walks up and says, “What did you get?” Are you going to say “Nothing” or “Zero”? Or are you more inclined to use a word that has a similar onset but is otherwise like punching the air – “Nada, niente, zip, zilch”?
Funny thing, isn’t it, how N and Z are really the same basic form at 90-degree rotation, but their feel and effect differ so much, thanks to their sound (the /n/ so soft and nasal, the /z/ buzzing, though both are done with the tongue in the same place), their relative frequency (n being the fifth most frequent letter in English, z being the least frequent – the [z] sound is more often represented with s because it used to be just an allophone of /s/), and perhaps the shape of their half-uncials (n rounded, z just as sharp as the capital).
But nada and niente are actual words for “nothing” in other languages, whereas zip and zilch are slang terms just in English. Their use for “zero” certainly can be reasonably suspected to be related to the /z/ onset. The dismissing flick of zip for “zero” (specifically on a test) showed up around 1900, about a quarter century after the word first arrived as onomatopoeia for a light, sharp sound of a fast-moving object and about a quarter of a century before it was applied to a clothing fastener. It may give you the feeling of an exam paper being flicked into the trash.
Zilch, on the other hand, will more likely give you the feeling of the paper being ditched into the dirt, or perhaps of the test taker himself being jettisoned into a gulch (where he is squelched by mulch). It doesn’t stop abruptly like zip; it curls into the impact and then slides a bit. (Or is that the sound of a paper being crumpled up?) It’s sort of like zero plus nil plus scratch, though that’s not likely where it came from.
So where did it come from? Well, it showed up in the 1960s, and a clear origin hasn’t been traced. It’s suggested that it comes from a character in a 1930s humour magazine called Ballyhoo, and there may be a connection to Joe Zilsch, a 1920s nickname for an average student – or a nonentity or loser. (Zilsch and Zilch are real family names; Oxford says they’re German/Slavic, while some other sources specify Yiddish.) But there’s a gap of a couple of decades between Ballyhoo and the “nothing” sense – not impossible, since someone might have spotted it in an old magazine and pressed it back into service (or might we say filched it). But as far as conclusive evidence goes, we have, well, zilch.