Strong's G4901 — συνεπιμαρτυρέω (verb)
sunepimartureo (soon-ep-ee-mar-too-reh'-o) v.
1. to testify further jointly, i.e. unite in adding evidence
[from G4862 and G1957]
KJV: also bear witness 
Root(s): G4862, G1957 
Hebrew root: ἐπιμαρτυρέω
Occurrences: 1