In the radical list, 癶 is listed as having the meaning "dotted tent."

Um ... what's a dotted tent?

It's a pair of opposite feet according to the etymology:

http://chineseetymology.org/CharacterEtymology.aspx?submitButton1=Etymology&characterInput=%E7%99%B6

Contrary, running counter, according to zdic.net:

http://www.zdic.net/zd/zi/ZdicE7Zdic99ZdicB6.htm

The bottom part of 舞?

It's the standard name for this radical:

http://en.wiktionary.org/wiki/Index:Chinese_radical/%E7%99%B6

I'm just as mystified as you are.

范博涵, the bottom part of 舞 is a different radical (舛). When 癶 is used, it can be seen pretty clearly. For example, 登.

I saw the two feet etymology, which makes sense. I'm not exactly sure where this dotted tent thing comes from, although I've seen it on other sites as well, like http://www.yellowbridge.com/chinese/radicals.php

Well, it does look a bit like a tent opening with dots on the side. I guess that, for some, it may be easier to remember that way than "opposing feet". But incorrect.

Haha so I just looked up te name for this radical in Japanese, and it's totally just referred to by its sound (hatsu, ハツ). In korean, it's referred to as the top (crown) of 発. It seems like each language just makes up its own new name/meaning for it, regardless of what's meaning was originally in Chinese, because radicals like these are so rarely used.