Is checkedness a word?

In the W3C HTML 5 specification, there are a number times the word checkedness is used, the following is where each word links to when used:

Form controls have a value and a checkedness.

Is checkedness a technical term or a word defined in a dictionary as I’m unable to find it in both UK and US dictionaries and I’m unsure of what it means?

If it is a word can a definition be provided.