Vincent's NT Word Studies
26. Failing (apoyucontwn). Only here in New Testament. The word originally means to leave off breathing; to swoon. Thus Homer, when Laertes recognizes Ulysses:"He threw Round his dear son his arms. The hardy chief, Ulysses, drew him fainting (apoyuconta) to his heart." Odyssey, xxiv., 346.
So also Sophocles, of Hector dragged behind Achilles' chariot:
"He breathed out his life (apeyuxen bion).
Ajax, 1031.
Matthew alone uses the simple verb, yucw, to breathe, or blow. See on wax cold, Matt. xxiv. 12. Luke uses four compounds of this simple verb, all of which are peculiar to him. Compare cool, ch. xvi. 24; refreshing, Acts iii. 19; gave up the ghost, Acts v. 5, 10.
Expectation (prosdokiav). Only here and Acts xii. 11.
The world. See on ch. ii. 1.
Shall be shaken (saleuqhsontai). Compare Matt. xi. 7; Luke vi. 38; Acts iv. 31; Heb. xii. 26, 27. The root of the verb is the same as that of billows, ver 25.
Robertson's NT Word Studies
21:26 {Men fainting} (apoyucontwn anqrwpwn). Genitive absolute of apoyucw, to expire, to breathe off or out. Old word. Here only in N.T. {Expectation} (prosdokias). Old word from prosdokaw, to look for or towards. In the N.T. only here and #Ac 12:11. {The world} (tei oikoumenei). Dative case, "the inhabited" (earth, gi).