The Greek verb diischyrizomai means to insist strongly, affirm confidently, or maintain something with certainty. The compound of dia (thoroughly) and ischyros (strong) suggests an emphatic, firm assertion — standing by one's testimony under pressure.
In Acts 12, the servant girl Rhoda diischyrizomai — she insists with full confidence that Peter is at the door, even when the believers she tells refuse to believe her. The word also appears in Luke 22:59 when bystanders insist that Peter was with Jesus. Ironically, diischyrizomai is used for true testimony that is doubted (Rhoda) and for false identification that is true (Peter's association with Jesus). The word underscores the importance of bold, confident testimony — and the human tendency to doubt the very answers to our own prayers.