Éibhear

I know what that tribe's name means! It HAS to mean "the Hebrew [tribe of] Dan." Dan was the ancestor of the Celtic tribes. That said, Eibhear comes from the name Eber, which means, "region beyond," from the Chaldean/Hebrew word abar, which means, "to pass over." Eber is the ancestor of Abraham, who is the ancestor of the Arabs and the tribes of Israel. The name Eber is where we get the name Hebrew.

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Another name for the ancestors of the Celts is Tuaath Danaan, which means, "tribe of Dan." Dan means, "Judge," and has its own entry on this site.

Yeah, that's not where the Celts came from. Celtic linguistic heritage traces back to the Urnfield culture in modern western/central Europe and predates any possible existence of Jacob or his sons.

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Eibhear is the modern Irish word for granite, but it's hard to say if there is any connection. I would wonder if it's not a cognate of Iberian, as Eibhear Finn and Eibhear Dunn were from the Iberian Peninsula. It could have meant, roughly, "the white/light Iberian," and "the brown/dark Iberian."