fraternity (n.)

early 14c., "body of men associated by common interest," from Old French fraternité (12c.), from Latin fraternitatem (nominative fraternitas) "brotherhood," from fraternus "brotherly," from frater "brother," from PIE root *bhrater- "brother." Meaning "state or condition of being as brothers" is from late 15c. College Greek-letter organization sense is from 1777, first in reference to Phi Beta Kappa.