Strong's G731 — ἄρῥητος (adjective)
arrhetos (ar'-rhay-tos) adj.
1. unsaid
2. (by implication) inexpressible
[from G1 (as a negative particle) and the same as G4490]
KJV: unspeakable 
Root(s): G1, G4490 
Hebrew root: ῥητῶς
Occurrences: 1