In a nearly 13-minute address, he did not tip his hand about what he might do next.

I seem to recall that this very question was discussed and answered on one of the linguistics blogs in the past couple of months. It may have been on Language Log, but I'mn't sure. I think the answer was that it arose as a shortened form of amn't I.

My mother warned me not to squirrel around in my dad's workshop.

Thus, although this department was among the more volatile fluctuators between regular and cutback budgets, the overall effect on the department suggests that growth was nearly static.