pedant n.

late 14c., pedagoge, "schoolmaster, teacher of children," from Old French pedagoge "teacher of children" (14c.), from Latin paedagogus, from Greek paidagōgos "slave who escorts boys to school and generally supervises them," later "a teacher or trainer of boys," from pais (genitive paidos) "child" (see pedo-) + agōgos "leader," from agein "to lead" (from PIE root *ag- "to drive, draw out or forth, move").

"[N]ow used, generally with a sense of contempt, for a dogmatic and narrow-minded teacher" [Century Dictionary, 1895]; the hostile implications in the word are from at least the time of Pepys (1650s). Related: Pedagogal.

"making an undue or inappropriate display of learning, absurdly learned," formed in English c. 1600, from pedant + -ic. The French equivalent is pédantesque. Perhaps first attested in John Donne's "Sunne Rising," where he bids the morning sun let him and his love linger in bed, telling it, "Sawcy pedantique wretch, goe chide Late schooleboyes." Related: Pedantical (1580s); pedantically.