Both seem to be used in web development circles, see e.g. HTML5 Cross Browser Polyfills, which says:
So here we’re collecting all the shims, fallbacks, and polyfills…
Or, there’s the es5-shim project.
In my current project we’re using a number of these, and I want to stick them all in the same directory. So, what should I call this directory—shims, or polyfills?