Origin: 1400–50 in sense “segregated”; 1535–45 as transitive v.; late Middle Englishsegregat < Latinsēgregātus (past participle of sēgregāre to part from the flock), equivalent to sē-se- + greg- (stem of grex flock) + -ātus-ate1; see gregarious
1540s, from L. segregatus, pp. of segregare "separate from the flock, isolate, divide," from *se gregare, from se "apart from" (see secret) + grege, ablative of grex "herd, flock." Originally often with reference to the religious notion of separating the flock of the godly from sinners.