Why is the ninth month called September?
late 15c., from Middle French convalescence (15c.), from Late Latin convalescentia "regaining of health," from convalescentem (nominative convalescens), present participle of convalescere (see convalesce).
convalescence con·va·les·cence (kŏn'və-lěs'əns)
Gradual return to health and strength after an illness, an injury, or a surgical operation.
The period needed for returning to health after an illness, an injury, or a surgical operation.