A portmanteau of "flail" and "arm". To flarm is to swing one's arms about wildly in a spastic manner, usually as an expression of surprise, amazement, or joy.
The excess skin that hangs on the underside of the upper arm, typically found on older, oftentimes overweight people. Derived from "Flabby Arm" = Flarm
As a child, I used to enjoy shaking the flarm on my mother's arm and watch it wigglelike jello.