So I e-mailed my sister last night and asked her if she remembered which Scottish clan we belong to (she was big into family trees a few years back), and I just heard back from her. It turns out that we're most likely descended from the Murray clan, and from a little bit of googling about said clan, I found this:

Motto: Furth, Fortune, and Fill the Fetters - go forth against your enemies, have good fortune, and return with hostages and booty

How fucking awesome is that? Best motto ever!

Although our tartan is kind of ugly. Ah well. ;3 I never did claim I was one for fashion.