BIFAST
sagnorð
ð, mod. að, dep. [Gr. φεβ-, φόβος, cp. Lat. paveo, febris; A. S. beofan; Germ. beben], to shake, to tremble:
1. in old writers only dep., bifðisk, Þkv. 13, Hkv. 23, Þd. 17; bifaðist, Gísl. 60, Grett. 114: to fear, en þó bifast aldri hjartað, Al. 80.
2. in mod. usage also act. to move, of something very heavy, with dat., e. g. eg gat ekki bifað því, I could not move it.