From epi and ischuo; to avail further, i.e. (figuratively) insist stoutly -- be the more fierce.
see GREEK epi
see GREEK ischuo
1. transitive, to give additional strength; to make stronger (Sir. 29:1; Xenophon, oec. 11, 13).
2. intransitive, to receive greater strength, grow stronger (1 Macc. 6:6; Theophr, Diodorus): ἐπίσχυον λέγοντες, they were the more urgent saying, i. e. they alleged the more vehemently, Luke 23:5.