tribe

mid-13c., "one of the twelve divisions of the ancient Hebrews," from Old French tribu, from Latin tribus "one of the three political/ethnic divisions of the original Roman state" (Tites, Ramnes, and Luceres, corresponding, perhaps, to the Latins, Sabines, and Etruscans), later, one of the 30 political divisions instituted by Servius Tullius (increased to 35 in 241 B.C.E.), perhaps from tri- "three" + *bhu-, root of the verb be. Others connect the word with the root of Welsh tref "town, inhabited place."

In the Biblical sense, which was the original one in English, the Latin word translates Greek phyle "race or tribe of men, body of men united by ties of blood and descent, a clan" (see physic). Extension to any ethnic group or race of people is first recorded 1590s.