mid-13c., "happiness," also "prosperity in abundance of possessions or riches," from Middle English wele "well-being" (see weal (n.1)) on analogy of health.
Entries linking to wealth
weal n.1
"well-being," Old English wela "wealth," in late Old English also "welfare, well-being," from West Germanic *welon-, from PIE root *wel- (2) "to wish, will" (see will (v.)). Related to well (adv.).
health n.
Old English hælþ "wholeness, a being whole, sound or well," from Proto-Germanic *hailitho, from PIE *kailo- "whole, uninjured, of good omen" (source also of Old English hal "hale, whole;" Old Norse heill "healthy;" Old English halig, Old Norse helge "holy, sacred;" Old English hælan "to heal"). With Proto-Germanic abstract noun suffix *-itho (see -th (2)).
Of physical health in Middle English, but also "prosperity, happiness, welfare; preservation, safety." An abstract noun to whole, not to heal. Meaning "a salutation" (in a toast, etc.) wishing one welfare or prosperity is from 1590s. Health food is from 1848.