Etymology Dictionary

FAST (1),  firm, fixed.  (E.)   M.E. fast, Ormulum, 1602; as adv. faste, Chaucer, C. T. 721.—A.S. fæst, Grein, i. 271. + Du. vast. + Dan. and Swed. fast. + Icel. fastr. + O.H.G. vast; G. fest.   Cf. Gk. ἔμ-πεδ-ος, fast, steadfast.   The Lat. op-pid-um, a fastness, fort, town, has the same root.   Connected with Fetter and Foot, q.v.   See Curtius, i. 303, 304.   Der. fast, verb (below); fast-en, q.v.; fast-ness, q.v.   ¶ The phrase 'fast asleep' is Scandinavian; Icel. sofa fast, to be fast asleep; see Fast (3).

FAST (2),  to abstain from food.  (E.)   M.E. fasten, Wyclif, Matt. vi. 16.—A.S. fæst, Matt. vi. 16. + Du. vasten. + Dan. faste. + Swed. and Icel. fasta. + Goth. fastan. + G. fasten.   β. A very early derivative from Teutonic fast, firm, observe, be strict.   See Fast (1).   Der. fast, sb., fast-er, fast-ing, fast-day.

FAST (3),  quick, speedy.  (Scand.)   Merely a peculiar use of fast, firm.   Chaucer has faste = quickly; C. T. 16150.   The peculiar usage is Scandinavian.   Cf. Icel. drekka fast, to drink hard; sofa fast, to be fast asleep; fylgja fast, to follow fast; fastr í verkum, hard at work; leita fast eptir, to urge, press hard after.   The development is through the senses 'close,' 'urgent.'   See Fast (1).