Fnǽstian

According to the Old English Dictionary:

fnǽstian

p, ode To breathe hard, pant :-- Þá men beóð mægre . . . fnǽstiað swíþe (breathe with great difficulty), Lch. ii. 242, 7. [N. E. D. fnast. O. H. Ger. fnástón anhelare.] fnæstian