At Snp 1.7 we find the Vasala Sutta, often translated as the “Outcaste” by such luminaries as Ven Bodhi and KR Norman. The basic meaning of vasala appears to be “wretch”, and that is how I have translated it throughout. The term “outcaste” has, of course, a specific meaning in India: one who is rejected from and outside of the four castes recognized by the brahmins. Normally in Pali this would be caṇḍāla. Neither Norman nor Bodhi offer a justification for translating vasala as “outcaste”, and the usage elsewhere in the canon doesn’t seem to support it.
- Ud 3.6: A monk calls other monks vasala (because of past life predelictions), there’s no hint caste is involved.
- MN 93, some brahmin sages curse an interloper as vasala; here caste is a topic, but there’s still no explicit reason to think vasala means “outcaste” and Ven Bodhi translates as “wretch”.
- SN 7.1: a brahmin husband angry with his wife calls her vasala, but she’s a brahmin.
The Sanskrit usage doesn’t support a meaning of “outcaste”; normally it just means “wretch” etc., and where it does have a caste association it is with a śūdra, i.e. low caste, not outcaste.
The sutta concludes with a set of comparisons of the kind found commonly, saying one is not a brahmin by birth, nor is one a vasala by birth, but by deeds. This certainly suggests that a vasala is defined at least in part by birth, although “low caste” would fit just as well. The Indian caste system was not so clearly defined in the time of the Buddha, and I think this was a word that had a general meaning of “wretch” that could come to be loosely applied in a caste-ish way, rather than being a specifically caste-defined term.