The element ether, called “akasha” in Sanskrit is the first of the five great elements (pancha mahabhutus). It comes first because it is the most subtle of the elements. Often referred to as “space,” it is the essence of emptiness. It is the space the other elements fill. The origin of ether is shabda. Shabda is the tanmatra of sound, meaning that shabda is sound in its primordial, unmanifested form. Shabda is the primordial space from which vibration emerges long before it takes the form of sound in the ear. Sound and ether are inseparable.
https://www.ayurvedacollege.com/blog/five-elements-ether-ayurveda/