Why is the ninth month called September?
late 14c., from Latin inveteratus "of long standing, chronic," past participle of inveterare "become old in," from in- "in, into" (see in- (2)) + veterare "to make old," from vetus (genitive veteris) "old" (see veteran).
inveterate in·vet·er·ate (ĭn-vět'ər-ĭt)adj.
Firmly and long established; deep-rooted.
Persisting in an ingrained habit; habitual.