Why is the ninth month called September?
"pertaining to or descended from the mother's side," 1897, from matri- + lineal. Related: Matrilineage; matrilineally.
matrilineal mat·ri·lin·e·al (māt'rə-lĭn'ē-əl)adj. Relating to, based on, or tracing ancestral descent through the maternal line.
Tracing kinship and descent through the female line. (Compare patrilineal.)