Strong’s Greek
G1957 — epimartureo
The entry below is Strong’s own definition (1890, public domain), and every verse where the word occurs.
ἐπιμαρτυρέω
epimartureo — pronounced ep-ee-mar-too-reh'-o
from 1909 and 3140; to attest further, i.e. corroborate:--testify. see GREEK for 1909 see GREEK for 3140
1 occurrence in the KJV.
1 Peter 5:12
By Silvanus, a faithful brother unto you, as I suppose, I have written briefly, exhorting, and testifying that this is the true grace of God wherein ye stand.