The universal progenitor is a late arrangement, but the name is not. Kashyapa occurs in the Vedic corpus before any of that structure exists, and it survives in a place that has nothing to do with mythology at all: Kashyapa is one of the principal brahmin gotras, the exogamous lineages that trace descent from a founding seer, and it is among the most widely borne of them. A very large number of living families carry the name as an ancestor claim, which is a form of continuity quite different from worship.
The etymology is the interesting and unresolved part. Kashyapa is also an ordinary Sanskrit word for a tortoise, and the identification of the sage's name with that word is old. It is attractive because the tortoise is a creation figure elsewhere in the same literature, where Prajapati takes the form of a tortoise, and a progenitor who is also a tortoise would tie two strands together neatly. It is not secure. The two words may be homonyms, and a resemblance that suits a later theology is exactly the kind of thing a later theology is capable of producing. The atlas marks the identification as argued.
One more thing needs saying because the name is crowded. The Buddhist tradition has a Kassapa who was among the closest disciples of the Buddha and presided over the first council, and a Kassapa who was a Buddha of a previous age. Neither is this figure. They share a name that was common enough to belong to several traditions at once, and conflating them is an easy mistake to make from an index.