τὠποβαῖνον
From LSJ
οἱ τοῖς πέλας ἐπιβουλεύοντες, λανθάνουσι πολλὰκις ὑφ' ἑτέρων τοῦτ' αὐτὸ πάσχοντες → when people plot against their neighbours, they fall victim to the same sort of plot themselves
crase ion. p. τὸ ἀποβαῖνον.
τὠποβαῖνον: in crasi ион. = τὸ ἀποβαῖνον.