No, my friend, smegma is and has been a word and it has a meaning.

They chose it as an obscure and disgusting word to use as an insult.

Smegma is the thick, white, cheesy substance that collects under the foreskin of the penis.

So if you're uncircumsized, and have ever not washed your dick in a few days, you're intimately familiar with what smegma is.

It is categorically not a made-up "future swear."