Pani Dasyu is a rich person who does not care to make offerings to the gods or give fees to the priests. The person is mentioned in some hymns of Rig Veda.
Pani Dasyu – s are spoken of as niggardly and as wolves, full of bestial vanity. Some of the western scholars agree with this interpretation, while the traditional commentators interpret the word as barter.
Some other hymns of Rig Veda make mythological references to the pani-s as demons withholding the waters of heaven.
Frequently, pani-s are mentioned as opponents of Divodasa Atithigva, one of the leading princes of the Vedic age and as the thieves who stole the cattle of the Aryans.
In one hymn pani-s are referred to as dasyu-s, apparently meaning of hostile speech.
There are divergent views about the exact significance of the words pani and dasyu.
In classical Sanskrit, the word pani denotes the market, the root pan conveys the sense of bartering, bargaining, or betting and the word pana, the sense of playing with dice.
Since the dasyus have been described as not performing rituals, not worshipping gods, practicing strange rites and so on, the panis are considered niggardly and equated with the dasyus.
Some scholars also suggest that the panis were Semitic traders.
Nevertheless, Rig Veda refers to both pani and dasyu with unconcealed derogation.
Source:
Vedic Index Vol I (1995) A A Macdonell and A B Keith - Motilal Banarsidass New Delhi
Encyclopedia of Hinduism Volume VIII page 50 - IHRF