What's the difference between i.e. and e.g.?
Old English fæst "firmly fixed, steadfast, secure, enclosed," probably from Proto-Germanic *fastuz (cf. Old Frisian fest, Old Norse fastr, Dutch vast, German fest), from PIE root *past- "firm" (cf. Sanskrit pastyam "dwelling place").
The adverb meaning "quickly, swiftly" was perhaps in Old English, or from Old Norse fast, either way developing from the sense of "firmly, strongly, vigorously" (cf. to run hard means to run fast; also compare fast asleep), or perhaps from the notion of a runner who "sticks" close to whatever he is chasing.
The sense of "living an unrestrained life" (usually of women) is from 1746 (fast living is from 1745). Fast buck recorded from 1947; fast food is first attested 1951. Fast-forward first recorded 1948. Fast lane is by 1966; the fast track originally was in horse-racing (1934); figurative sense by 1960s. To fast talk someone (v.) is recorded by 1946.
Old English fæstan "to fast" (as a religious duty), from Proto-Germanic *fastejan (cf. Old Frisian festia, Old High German fasten, German fasten, Old Norse fasta), from the same root as fast (adj.).
The original meaning was "hold firmly," and the sense evolution is via "firm control of oneself," to "holding to observance" (cf. Gothic fastan "to keep, observe," also "to fast"). Presumably the whole group is a Germanic translation of Medieval Latin observare "to fast." Related: Fasted; fasting.
Old English fæstan, festen, or Old Norse fasta; from the root of fast (v.).
fast 1 (fāst)
adj. fast·er, fast·est
Acting, moving, or being capable of acting or moving quickly.
Accomplished in relatively little time.
Exhibiting resistance to change. Used especially of stained microorganisms that cannot be decolorized.
Firmly fixed or fastened.
v. fast·ed, fast·ing, fasts
To abstain from food.
To eat little or abstain from certain foods, especially as a religious discipline.
The act or practice of abstaining from or eating very little food.
A period of such abstention or self-denial.
Morally lax; libertine: on Long Island with the fast younger married set (1859+)
The sole fast required by the law of Moses was that of the great Day of Atonement (q.v.), Lev. 23:26-32. It is called "the fast" (Acts 27:9). The only other mention of a periodical fast in the Old Testament is in Zech. 7:1-7; 8:19, from which it appears that during their captivity the Jews observed four annual fasts. (1.) The fast of the fourth month, kept on the seventeenth day of Tammuz, the anniversary of the capture of Jerusalem by the Chaldeans; to commemorate also the incident recorded Ex. 32:19. (Comp. Jer. 52:6, 7.) (2.) The fast of the fifth month, kept on the ninth of Ab (comp. Num. 14:27), to commemorate the burning of the city and temple (Jer. 52:12, 13). (3.) The fast of the seventh month, kept on the third of Tisri (comp. 2 Kings 25), the anniversary of the murder of Gedaliah (Jer. 41:1, 2). (4.) The fast of the tenth month (comp. Jer. 52:4; Ezek. 33:21; 2 Kings 25:1), to commemorate the beginning of the siege of the holy city by Nebuchadnezzar. There was in addition to these the fast appointed by Esther (4:16). Public national fasts on account of sin or to supplicate divine favour were sometimes held. (1.) 1 Sam. 7:6; (2.) 2 Chr. 20:3; (3.) Jer. 36:6-10; (4.) Neh. 9:1. There were also local fasts. (1.) Judg. 20:26; (2.) 2 Sam. 1:12; (3.) 1 Sam. 31:13; (4.) 1 Kings 21:9-12; (5.) Ezra 8:21-23: (6.) Jonah 3:5-9. There are many instances of private occasional fasting (1 Sam. 1:7: 20:34; 2 Sam. 3:35; 12:16; 1 Kings 21:27; Ezra 10:6; Neh. 1:4; Dan. 10:2,3). Moses fasted forty days (Ex. 24:18; 34:28), and so also did Elijah (1 Kings 19:8). Our Lord fasted forty days in the wilderness (Matt. 4:2). In the lapse of time the practice of fasting was lamentably abused (Isa. 58:4; Jer. 14:12; Zech. 7:5). Our Lord rebuked the Pharisees for their hypocritical pretences in fasting (Matt. 6:16). He himself appointed no fast. The early Christians, however, observed the ordinary fasts according to the law of their fathers (Acts 13:3; 14:23; 2 Cor. 6:5).