[PyWoody]

If you go back even further, you get the iota subscript [0]

[0] https://en.wikipedia.org/wiki/Iota_subscript

[demetrius]

Iota subscript is a 12-century invention. Rough and smooth breathings (ἁ for ha, ἀ for a) are much older Greek diacritics.

For another example of classical diacritics, see apices in Latin (á for long a).