βεβαιόω
Etym. from βέβαιος
I. "to make firm, confirm, establish, secure, warrant, make good", Plat., Xen.; ἔργωι βεβαιούμενα "things warranted by fact", opp. to ἀκοῆι λεγόμενα, Thuc.
2. β. τί τινι "to secure" one "the possession of" a thing, id=Thuc.:—Mid. "to establish for oneself, to confirm, secure", id=Thuc.
II. Mid. also "to secure one's ground" in argument, "to asseverate, maintain, make good", Plat.
2. "to guarantee" a title, Isae.