convalescence (n.)

"a gradual recovery of strength and health after a sickness," late 15c., from French convalescence (15c.), from Late Latin convalescentia "a regaining of health," from convalescentem (nominative convalescens), present participle of Latin convalescere"thrive, regain health, begin to grow strong or well," from assimilated form of com-, here perhaps an intensive prefix (see com-), + valescere "to begin to grow strong," inchoative of valere "to be strong" (from PIE root *wal- "to be strong"). Related: Convalescency.