1823, noun of action from hydrate (v.). Perhaps from French hydration.
Entries linking to hydration
hydrate v.
1812 (implied in hydrated), "to form a hydrate, combine chemically with water," from hydrate (n.), perhaps modeled on French hydrater. From 1947 as "to restore moisture;" from Greek hydr-, stem of hydor "water" (from suffixed form of PIE root *wed- (1) "water; wet") + -ate (2). Related: Hydrating.
rehydration n.
"process of adding or taking up water again," 1853, from re- "again" + hydration.