As I was looking up “unbated” on Etymology Online, I worked out for myself its roots. Of course…the opposite of unbated is bated. And bated is usually heard in relationship to breath, a withheld breath, a limited breath is bated. So a sword in fencing is usually bated – that is held back, blunted from its usual fullness to a limited version of itself. So this sword meant to kill Hamlet is unbated, un-leashed, unbound – the full expression of sword-ness.