Rennervate is the incantation for a spell used to revive a person, for example one who has been hit by a Stunning Spell.
References from the canon
- Amos Diggory woke up Winky with this (GF9)
- Dumbledore used it to revive Barty Crouch junior (GF35)
- Dumbledore also used it to revive Viktor Krum after he was stunned while watching over Barty Crouch senior (GF28).
- Harry uses this spell to revive Dumbledore after the Headmaster drank the potion in the stone basin where Voldemort hid the locket Horcrux (HBP26)
"en-" Old French from "in-" L. cause to be + "nerves" Eng. c.1603 strength, from "nervus" L. nerve
This spell has been officially renamed by JKR from its original name, Ennervate. Some versions list this spell as "Enervate," which changes the etymology quite a bit. "Enervate" means to take away energy while "Ennervate" means to give someone energy.