"regexp" is my guess, too. Mostly, I was trying to conform to the current naming scheme, and also jQuery's.

Regarding the RegExp itself: [I ripped it from the jQuery source directly](https://github.com/jquery/jquery/blob/626cbde7f8267e2463cef85d84f9f0172f1c7cb9/src/data.js#L20) so that we would match behavior as closely as possible.