Why is the ninth month called September?
1610s, from French hymen (16c.), from medical Latin, ultimately from Greek hymen "membrane (especially 'virginal membrane,' the membrane par excellence); thin skin," from PIE *syu-men-, from root *syu- "to bind, sew" (see sew). Originally any membrane; present specific meaning begins with Vesalius in the 1555 edition of De humani corporis fabrica. Apparently not directly connected to Hymen, the god of marriage, but sharing the same root and supposed to be related in folk etymology.
hymen hy·men (hī'mən)
A membranous fold of tissue that partly or completely occludes the external vaginal orifice.
The Greek god of the wedding feast.
Note: An apparently intact hymen is valued in some cultures as proof of virginity in a bride; this “proof,” however, is not accurate. The hymen may appear incomplete in a virgin, and it may appear intact in a woman who has engaged in sexual intercourse.