I looked up “argal” in the dictionary – it says “therefore.”
Which, I knew…but my question wasn’t really what was meant here – it was “Is this a joke?”
Like – it feels to me that it’s possible that the gravedigger/clown means to say “ergo” and gets it wrong.
But there is this circularity in language and Shakespeare. We get words from Shakespeare so we define them by what the word is doing in Shakespeare’s text – meanwhile, the word may have been invented by Shakespeare, or was a common joke, or a slang version of something. And what once was a joke might become an actual word that serious literary people use as an alternative to “Ergo.”
The Hamlet Project 