TV's Frink said:
The quotation marks are typos. Ahhrghugh means "rip an arm out of a socket" in Old English.
Mistakes, yes. Typos, no. Just another instance of the systemic sloppiness that hangs all over that shirt design like the BO of the shirt's obese wearer most certainly does after it gets tossed into the hamper to await mom's laundry day.
The intent was clearly that "Hrryauhg" or whatever was a Wookiee-language substitute for an English-language predicate that would grammatically parallel the rest of the captions. Much like the Bee-yoop for R2. But note the embarrassing inconsistency between the un-quoted R2 phrase and the quotation-mark-marred Chewie phrase.
Just an absolute mess is this shirt, really.