Strong's G4517 — ῥώννυμι (verb)
rhonnumi (rhone'-noo-mee) v.
1. to strengthen
2. (impersonal passive) have health (as a parting exclamation, good-bye)
[prolongation from rhoomai "to dart" (probably akin to G4506)]
KJV: farewell 
See also: G4506 
Occurrences: 1