In Kassapa Buddha’s time she had been a nun well-
It has been suggested (VT.iii.360, n.3; and VT.ii.195‑6, n.3) that her name “half kāsī” might mean that she charged five hundred pieces from her patrons. For, according to Buddhaghosa, kāsī means one thousand, and anything worth one thousand is called kāsiya.
Another explanation is, however, given by Dhammapāla (ThigA.32). The revenue which accrued to the king for one day from Kāsī was a thousand. Aḍḍhakāsī’s patrons had to give a like sum to spend a night with her. This is referred to in one of the verses attributed to her in the Theragāthā (v.25). For this reason she was called Kāsī. However, later, many men, not being able to afford a thousand, would pay half the amount and spend the day with her. As a result she became known as Aḍḍhakāsī.