WordNet (r) 3.0 (2006):

fag end
    n 1: the time of the last part of something; "the fag end of
         this crisis-ridden century"; "the tail of the storm" [syn:
         fag end, tail, tail end]
    2: the frayed end of a length of cloth or rope

Moby Thesaurus II by Grady Ward, 1.0:

65 Moby Thesaurus words for "fag end":
   Thule, Ultima Thule, afterglow, afterimage, balance, bitter end,
   bottom dollar, boundary, butt, butt end, candle ends, chaff,
   debris, detritus, end, extreme, extremity, farthest bound, filings,
   fossil, holdover, husks, jumping-off place, leavings, leftovers,
   limit, nib, odds and ends, offscourings, orts, parings, point,
   pole, rags, refuse, relics, remainder, remains, remnant, residue,
   residuum, rest, roach, rubbish, ruins, rump, sawdust, scourings,
   scraps, shadow, shavings, straw, stub, stubble, stump, survival,
   sweepings, tag, tag end, tail, tail end, tip, trace, vestige,
   waste