Salvio hexia

Salvio Hexia is a protective spell whose effects are unclear, though - given the etymology - it appears to protect against hexes.

Known uses
Hermione Granger casted this protective spell on the campsite she shared with Harry Potter and Ron Weasley in 1997. Harry Potter would occasionally cast this spell during the horcrux hunt as well.

Behind the scenes

 * This may be a form of hex-deflection, though it remains uncertain if this was the spell that the fake Alastor Moody taught his fourth year Defence Against the Dark Arts students.

Etymology
The first word Salvio could come from either of the Latin words salvare (to save/protect), salveo (to be well/in good health) or salvus (safe and sound). Hexia is simply a Latinisation of the word "hex". Altogether, this may be taken to mean something akin to "safe from hexes"

Appearances

 * Harry Potter and the Deathly Hallows 
 * Harry Potter and the Deathly Hallows: Part 1

Notes and references
Salveo maleficia