The name of the bird is derived from its allegedly fearful nature. This etymology must be the result of an erroneous interpretation of a derivation advocated by Herodian, with a *πτῶ, future *πτήσω "to fly", synonym of πέτομαι and designed to account for the forms with -η- (πτηνός, πτῆσις):  see Etym. Magnum, Kallierges, p. 666 (ὁ δὲ Ἡρωδιανὸς, ἐκ τοῦ πετῶ πετάσω, πτῶ πτήσω πτηνὸν καὶ πετηνόν) (see πετεινός / πέτομαι). But the compiler did not understand and mistook this πτήσω for πτήσσω "to crouch for fear", hence the translation φοβοῦμαι.