What is "drvaspa"

Drvaspa (druuāspā, drvāspā, drwāspā) is the Avestan language name of an "enigmatic" and "strangely discreet" Zoroastrian divinity, whose name literally means "with solid horses" and which she is then nominally the hypostasis of.

The word drvaspa is grammatically feminine. Proceeding from an observation in James Darmesteter's Avesta (1875), "it has been customary to compare her to the Celtic Epona."