Literally Frankish, presumably abbreviated from ascia francisca (although securis is the more usual word for a battle-axe, we may infer ascia from the fact that gender congruence would not allow securis francisca), Frankish axe: the characteristic throwing-axe of the Franks. Clovis, begetter of the Merovingians, famously threw his to mark out the length of the nave of the church which he would build to the glory of the kindly God who let him defeat the Goths in the battle on the Vocladian Fields, where he himself slew with his own hand Alaric, their chief.
It is not known exactly what manner of weapon this axe was; in former times it was often depicted as double-bitted, on the assumption that it would be more likely thus to pay a wound, and because the historian Procopius describes them thus, but several surviving axeheads have now been found, with a single bit and a characteristic falling butt. More recently, we've seen a theory that it had a long shaft, so constructed as to make it bounce when it hit hard ground; this, the proponents of the theory say, would have produced a great deal of disorder among the enemy when the axes were hurled en masse. But against this theory also we might hold ourselves skeptical, because it seems clear that if you wish to reach above your enemy's shield, simply throwing in an arc is better, and that much of the force of the throw will be lost in a bounce. It's more likely that, as Procopius also claims, the francisca would have had a very short, hatchetlike shaft, like a tomahawk; easily worn in the belt, easily drawn, and bad enough for the man on the wrong end.