convalesce (v.)

"to grow better after sickness, make progress toward the recovery of health," late 15c., from Latin convalescere "thrive, regain health, begin to grow strong or well," from assimilated form of com-, here probably an intensive prefix (see com-), + valescere "to begin to grow strong," inchoative of valere "to be strong" (from PIE root *wal- "to be strong"). Only in Caxton and Scottish writers until 19c. Related: Convalesced; convalescing.