Zareth posted...
And why would you name a character for a restaurant chain after an expression of disgust?
Because he was supposed to be a bad guy. Like the Hamburglar.
Hamburglar stole burgers, Grimace was supposed to steal milkshakes.
Also - and this is just supposition on my part - you could argue that people make a grimace when they get ice cream headaches, so that's like the evil side of milkshakes. So maybe that was the motivation for the name, because they couldn't think of a pun like with Hamburglar.