Why is the ninth month called September?
late 14c., "pertaining to a single thing or person," from Old French particuler (14c., Modern French particulier) and directly from Late Latin particularis "of a part, concerning a small part," from Latin particula "particle" (see particle). Sense of "precise, exacting" first recorded 1814.
"a part or section of a whole," late 14c., from particular (adj.). Particulars "small details of statement" is from c.1600.