Meaning

noun (plural) the lay members of a male religious order

noun a male with the same parents as someone else

noun a male person who is a fellow member (of a fraternity or religion or other group)

originFrom Early Modern English brethren, plural of brother, from Middle English brethren, from Middle English brethere, brether + -en (plural ending). Ultimately from Old English brōþor, brōþru (“brothers, brethren”), influenced by Old English brēþer, dative singular of brōþor (“brother”). Equivalent to brother + -en (plural ending). Compare German Brüder (“brothers, brethren”). More at brother. The…

Etymology from Wiktionary, CC BY-SA 3.0