HTML5 Shim vs. Shiv

It was originally called the html5-shiv.

Shiv really isn't the right term, as a shiv is a stabbing-implement.

A shim is something which you use to level things out (or prop them up). If a table has one leg that's too short, you might shim it with a piece of wood or a phone book...

So html5-shim is for people who expect html5shiv to be called a shim.

That's entirely it, as far as differences go.

Kind of like polyfills cover over the differences in implementations of features.
In North America, Polyfill might be called "Spackle".

From http://code.google.com/p/html5shim/

shiv or shim?

Common question: what's the difference between the html5shim and the html5shiv?
Answer: nothing, one has an m and one has a v - that's it.

The answer is.

The term shiv originates from John Resig, who was thought to have used the word for its slang meaning, a sharp object used as a knife-like weapon, intended for Internet Explorer. Truth be known, John probably intended to use the word shim, which in computing means an application compatibility workaround. Rather than correct his mispelling, most developers familiar with Internet Explorer appreciated the visual imagery. And that, kids, is etymology.

From author's page at https://github.com/aFarkas/html5shiv