stickler (n.)

1530s, "moderator, umpire," agent noun from stickle "mediate" (1520s), probably a frequentative of Middle English stighten "to arrange, place," from Old English stihtan "to rule, direct, arrange, order," which is cognate with Middle Dutch stichten, German stiften "to found, establish," probably from Proto-Germanic *stihtan "to place on a step or base," from PIE root *steigh- "to stride, step, rise" (see stair). Meaning "person who contends or insists stubbornly" is first recorded 1640s.