ἔν-δειγμα, -τος (< ἐνδείκνυμι), a plain token, proof: 2Th.1:5 (cf. ἔνδειξις, which refers rather to the "act of proving"; ἔ., with the passive formation, to the thing proved, see Lft., Notes, 100; M, Th., l.with).† SYN.: τεκμήριον (AS)
Thayer:
1) token, evidence, proof
ἔνδειγμα
endeigma
en'-dighe-mah
From G1731; an indication (concretely)