Why is the ninth month called September?
late 14c., from Old French formacion (12c.) or directly from Latin formationem (nominative formatio) "a forming, shaping," noun of action or condition from past participle stem of formare "to form" (see form (v.)).
formation for·ma·tion (fôr-mā'shən)
The act or process of forming something or of taking form.