The earliest interpretation of the Symbol ‘0’ was as Pūjyam, a mystical expression marking: ‘That worthy of worship’.
From what little we know about its intended meaning it was a simultaneous reference to both a Completeness [the Plenum of the Iśopaniṣad] and one of Absence.
The meaning meanders over the subsequent centuries and around 500 BCE settles as Shūnyam, from a verbal root denoting hollowness [’empty inside’].
It then descends from the exalted heights of the Upaniṣads and Sūtras to its present status as inconspicuous character on a crowded keyboard.
And so here we are in our present Information Age where all Knowledge, so the scholars claim [nay, even all Wisdom], is captured in the Boolean Binary of ‘0,1’.
Shūnyam is the formal Sanskrit for Śūnya in common-speak. Etymologically, Shūnyam originate in the notion of hollowness, of ‘Empty Inside’.
The term ‘Empty’ or ‘Null’ as used in English translations of Shūnyam originate directly from the vocabulary of Classical Logic as does the word ‘Form’ as used in the Heart Sutra.
[Although no guru, fee-speaker or book-writer I have met is aware of this root, which might explain their wildly creative interpretations of these two terms.]
Shūnyam itself is not to be confounded with the numerous versions of Śūnya with a suffix that evolved in the regional Dharmic literatures well into the 10th Century [ŚūnyaBrahman, ŚūnyaPurusha et al].
Or the selective use of the term Shūnyathā in others, from the early Theravada Schools to the later Mahayana appropriations.