Where did about:blank get its name from?

about: is an internal URI scheme (also known as a "URL scheme" or, erroneously, "protocol") in various web browsers to display certain built-in functions. It is not an officially registered scheme, and has no standard syntax.

In early versions of Netscape, any address beginning about: which wasn't recognised as a built-in command would simply result in the text after the colon being displayed. Similarly, in early versions of Internet Explorer, about: followed by a string of HTML (e.g. about:hello world) would render that string as though it was the source of the page - thus providing a similar (though more limited) facility to the data: URI scheme defined by RFC 2397. Still other versions of Netscape would return various phrases in response to an unknown about: address, including "Whatchew talkin' 'bout, Willis?" (a catch phrase from the TV show Diff'rent Strokes) or "Homey don't play dat!" (from a recurring skit on the TV show In Living Color).

The most commonly implemented about: URIs are about:blank, which displays a blank HTML document, and simply about:, which may display information about the browser. Opera uses URIs beginning with opera: for similar purposes, and many about: URIs will be translated into an appropriate opera: URI if entered; an exception is about:blank, which is not translated.

Source

It's a generic name for the browser's about pages. I believe netscape was the first to use them, and they've caught on since then. A more technical explanation would be that about: is the protocol, and tells the browser what it's looking for is built in to the browser, no DNS or file requests necessary. Thusly, about:blank was used because about: was already programmed in, and less complexity means less bugs, and fewer potential security holes.