The name Hereswith is a girl's name meaning "Strength of the army". Hereswith and is often added to lists like Names That Mean Strong.
From the experts:
Hereswith is a rare name that comes to us from the dark ages. She was a Northumbrian saint, whose more famous sister, Hilda, was the Abbess at Whitby and patron of the first English poet, Caedmon. The name has a soft, lispy sound that is more wearable than its spelling would suggest.