The Pali word vaṇṇa has a wide range of meanings, as a glance at the dictionary entry will show. In a couple of verses in the Samyutta (SN 9.14#13 and SN 10.2#3), it is glossed by the commentary as kāraṇa (= “reason”). This strikes me as an unusual sense, so let’s investigate.
All the translators accept this sense (Bodhi, Thanissaro, CAF Rhys Davids, Olendzki), as does the Dictionary.
For SN 9.14, the Chinese texts support the sense of “reason”. SA 1338 has 何故 (“for what reason”, commonly used to render the term mentioned in the pali commentary, kiṃ kāraṇam), while SA2 358 has 以何因緣 in a similar meaning.
There are three Chinese parallels for SN 10.2. While I cannot be sure, it seems to me that these translations have 種 (SA2 299), 種姓 (SA2 162), and 生類 (SA 577) where the Pali has vaṇṇa; and that all these probably hark from an original vaṁsa rather than vaṇṇa. If they were from vaṇṇa, it would have been in the sense of “caste, social strata”. It’s not clear to me exactly how the sense of these verses work. I think it means, “If intimacy should arise with someone, no matter what class/strata of society they are from”. Perhaps @llt could help?
The PTS Dictionary also mentions three instances of this attested in later texts (Vv 84#6, Pv 36#6, and Pv 36#48). These are all phrased as a question (kena vaṇṇena), like SN 9.14 and unlike SN 10.2. In fact, this kind of phrasing is quite common in later verse.
The reading at Pv 36#48 seems to give the best sense for the idiom:
Atha tvaṃ kena vaṇṇena kimeva disvā
So for what vaṇṇa, seeing what
Here vaṇṇa relates to the idea of what data or information has been available, which is pretty close to the English idea “evidence”.
So it seems we should accept vaṇṇa in these places, but render more specifically as “evidence”. This works especially well in SN 9.14, as the monk is accused of being a “thief of scent”.
In SN 10.2, however, the idiom is different, and the sense is more likely to be “caste”.
On a less technical note, the sutta is a dialogue where a local deva accuses a monk of being a “thief of scent”. This is not the only striking image in the text. It’s the last text in this chapter, and was probably saved for this spot because it’s kind of awesome.
The monk replies to the accusation with a piece of classic “what-aboutery”, pointing to those who break flowers or dig them up. After all, all he does is enjoy the fragrance.
The deva has no time for this nonsense. She brushes off the blaming, saying she has nothing to say to such vandals, only to someone who is sincere. She memorably describes the vandals as being:
like a soiled nappy
Wow, that right there is a highly specific bit of metaphor. She captures not just the ugly side of vandalism, but the infantile, irresponsible attitude; and the waste of time it is to try to speak to such people.
The monk is eventually impressed, and asks the deva to help him out by admonishing him if she ever sees him do anything similar in the future. Now, in the Dhamma it is always a good sign to admit your faults, and to recognize the value of someone kind enough to point them out.
But once again, the deva has none of this. She says that she’s no dependent of his, nor his servant. It’s up to him to recognize such things for himself.
I think we can agree that this unknown deva just officially invented the “sick burn”.