Why is the ninth month called September?
mid-15c., "condition of being a father," from Old French paternité (12c.), from Late Latin paternitatem (nominative paternitas) "fatherly care, fatherhood," from Latin paternus "of a father," from pater (see father (n.)). Originally in the ecclesiastical sense; literal sense first recorded 1580s. Meaning "paternal origin" is from 1868.
paternity pa·ter·ni·ty (pə-tûr'nĭ-tē)
The state of being a father; fatherhood.
Descent on a father's side; paternal descent.