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.
tribe (trīb)
n.
An occasional taxonomic category placed between a subfamily and a genus or between a suborder and a family and usually containing several genera.
One's group of friends or relatives: dreading the tribe coming for New Year's
a collection of families descending from one ancestor. The "twelve tribes" of the Hebrews were the twelve collections of families which sprang from the sons of Jacob. In Matt. 24:30 the word has a wider significance. The tribes of Israel are referred to as types of the spiritual family of God (Rev. 7). (See ISRAEL, KINGDOM OF ØT0001909; JUDAH, KINGDOM OF.)