Fag, v. i. [imp. & p. p. Fagged; p. pr. & vb. n. Fagging.]
Etymology: [Cf. LG. fakk wearied, weary, vaak slumber, drowsiness, OFries. fai, equiv. to fach devoted to death, OS. f, OHG. feigi, G. feig, feige, cowardly, Icel. feigr fated to die, AS. f, Scot. faik, to fail, stop, lower the price; or perh. the same word as E. flag to droop.]
1. To become weary; to tire. Creighton withheld his force till the Italian began to fag. G. Mackenzie.
2. To labor to wearness; to work hard; to drudge. Read, fag, and subdue this chapter. Coleridge.
3. To act as a fag, or perform menial services or drudgery, for another, as in some English schools. To fag out, to become untwisted or frayed, as the end of a rope, or the edge of canvas.
2 other Webster entries under this spelling
Fag n.
A knot or coarse part in cloth. [Obs.]
Fag, v. t.
1. To tire by labor; to exhaust; as, he was almost fagged out.
2. Anything that fatigues. [R.] It is such a fag, I came back tired to death. Miss Austen. Brain fag. (Med.) See Cerebropathy.
Shades of meaning
Fernald has no entry of its own for fag; he lists it under tire.
He lists it without comment; the entries above explain its neighbors.