Strong's G1957 — ἐπιμαρτυρέω (verb)
epimartureo (ep-ee-mar-too-reh'-o) v.
1. to attest further, i.e. corroborate
[from G1909 and G3140]
KJV: testify 
Root(s): G1909, G3140 
Hebrew root: μαρτυρέω
Occurrences: 1