What was Big Willy Shakes going for?
Sly might be drunk, but he's easy to understand. This phrase means exactly what it says—he won't move at all from the alehouse. Not even an inch. It's supposed to overemphasize the fact that he's not going anywhere. Hyperbole, ladies and gentlemen.
Now of course it's ironic because moments later Sly passes out and gets taken away. Then he doesn't have control over where he's going, which incidentally is off to a lord's house to be tricked. That'll teach him about being nasty to the wait staff. (Or maybe not.)
This little charade makes for some raucous fun but it also opens up questions about the social disparity between the lower classes and the nobility. And it continues when Sly is victimized by a nobleman with a lot of money and the power and resources to make Sly question his whole identity.
Sly as a Lord? Please.
We also want to point out that Sly is the embodiment of the drunken theatergoer that people complained about in Shakespeare's day. He's drunk, disorderly, belligerent, and that's just in the first dozen lines of the play.
In many ways, this is Shakespeare's way of lovingly parodying the kinds of drunken theatergoers, or "groundlings," that sat in the cheap seats. Maybe Shakespeare is warning his audience in a tongue and cheek way to not overdo it, otherwise they, too, could be duped like silly old Christopher Sly.
While "not yield an inch" was around long before Shakespeare, his version of the phrase "budge an inch" has endured. Maybe it's because this whole episode with Sly is so memorable (and hilarious).