It’s important to note that the term “Dasyus” is a historical and cultural construct from ancient Indian texts, and it does not correspond directly to any specific ethnic or cultural group in modern times. The understanding of the Dasyus is primarily based on interpretations of the Rigveda, from different angles, by different historians from different backgrounds. Adequate evidence of origin of this word “Dasyus” during the long period in which they have formed an important element in the society of Ancient India is not available. The meaning of the word Dass is “A Real Man” and this has been described in the Khotanise dialect. The word “Dassa” is contained in the name of a famous Vedic kings also. Several other protagonist people in the Rig Veda also have “Dassa” in their name. Dassa also means “Heaven’s Slave” as per Rig Veda. These include Kings Sudasa and Grtsamadas. However the word slave was understood in a manner that Dasyus, were enemies of Aryans (the Nobles) This imagination gave birth to Aryan Invasion theory. But this theory lacked necessary evidences. Till last century Dass word, was used as a suffix with male child’s name in Hindu society. Dasyu is a term that could also be applied to Vedic kings. However the meaning of this term given in Rigveda was misunderstood by historians of western origin. They thought that the term is used to refer to a group of people who were considered adversaries/enemies of the Vedic civilization. In the battle of the Ten Kings in the Rig Veda, the king Sudass calls his enemies “Dasyu” though he himself carried Dass as suffix with his own name. While his enemies included Vedic peoples like the Anus, Druhyus, Turvashas, and even Purus, who also carried suffix Dass with their names. There is also mention of Dasa Balbutha Taruksa, who was a patron of a seer and who was distinguished by his generosity. There are several hymns in the Rigveda that refer to Dasa. As per Rigvedic verses, the Aryas and the Dasas stood united against their enemies. According to western origin historians, the Vedic texts describe battles and conquests of the Aryas over the Dasyus, which infact is a wrong interpretation of the text concerning Dasyus tribes. The Dasyus were depicted as people with different customs, languages, and religious practices. Dasyus were tree and serpent worshippers, and their principal deity was “Earth God”, to whom they offered human sacrifices.
According to western historians: “Dasyus seem too to have practised all kinds of worship, as most ancient Indians used to do, in their early state of civilisation. Presumably most of the Dasyus in India, converted to Budhism though Budha himself was a follower of Sanatana Dharma”
But the truth is that they were very much part of Sanatana Dharma society.
To conclude, meaning of one word Dass Slave was wss interpreted in a different manner by different historians.