Why is the ninth month called September?
1707, from bluster (n.) + -y (2). Blustering in this sense is recorded from 1510s.
late 14c., from a Low German source, e.g. Middle Low German blüstren "to blow violently," East Frisian blüstern "to bluster" (see blow (v.1)). Related: Blustered; blustering.
1580s, from bluster (v.).