From hupo and stello; to withhold under (out of sight), i.e. (reflexively) to cower or shrink, (figuratively) to conceal (reserve) -- draw (keep) back, shun, withdraw.
see GREEK hupo
see GREEK stello
1. Active, to draw down, let down, lower: ἱστίον, Pindar Isthm. 2, 59; to withdraw (draw back): ἐμαυτόν, of a timid person, Galatians 2:12 ((cf. Lightfoot at the passage); often so in Polybius).
2. Middle, to withdraw oneself, i. e. to be timid, to cower, shrink: of those who from timidity hesitate to avow what they believe, Hebrews 10:38 (from Habakkuk 2:4 (cf. Winers Grammar, 523 (487))); to be unwilling to utter from fear, to shrink from declaring, to conceal, dissemble: followed by τοῦ with the infinitive (Winers Grammar, 325 (305); Buttmann, 270 (232)), Acts 20:27; οὐδέν, ibid. 20 (often so in Demosthenes; cf. Reiske, Index graecit. Demosthenes, p. 774f; Josephus, Vita §54; b. j. 1, 20, 1).