DSL - SND1   CROTTLE, Crottal, Crotul, Cro(y)tal, n.1     1. A general term for the dye-producing lichens (Sc. 1825 Jam.2, crotal, crottle; Arg.1, Kcb.1 1941; Uls. 1880 W. H. Patterson Gl. Ant. and Dwn.); ``the dry lichen of the stone dykes, apt to stick to clothes laid on them'' (w.Dmf. 1899 J. Shaw in Country Schoolmaster (ed. Wallace) 346).
    *Sc. 1856 W. L. Lindsay Brit. Lichens iii.:
    In Scotland, not many years ago, particularly in certain districts, almost every farm and cotter-house had its tank or barrel of ``graith,'' or putrid urine (the form of ammoniacal liquid employed) and its ``litpig,'' wherein the mistress of the household macerated some familiar ``crottle'' (the Scotch vernacular term for the dye-lichens in general) such as Lecanora tartarea or Parmelia saxatilis, and prepared therefrom a reddish or purplish dye.
    *Cai. 1916 Old Cai. Croft in John o' Groat Jnl. (7 April):
    Sometimes the ``croytal'' or yellow growth on old dykes was boiled in ``rynded fat,'' then strained.
    *Ags.17 1941:
    There was --- and probably still is --- a superstition among fishermen on the West Coast that crottal seeks its native rocks and they were therefore averse to wearing garments dyed with crottal or to taking on board anyone so clad.
    *w.Sc. (Heb.) 1875 W. A. Smith Lewsiana 61:
    Amongst the dyes still in use is the grey moss called ``crotul,'' which covers the surface of the outcropping rocks throughout the country.

    Hence crottlie, lichen-covered (Ayr.4 1928, obs.).
    *Kcb. 1814 J. Train Mountain Muse 65:
    Or Morag's mournful ditty chimed, As o'er the crottlie crags they climb'd.

    2. The dye produced from the lichen.
    *w.Sc. 1927 Spectator (10 Sept.) 379/2:
    Dyes for the homespuns, heather making a wonderful yellow and a lichen from the rocks a rich brown, known as crottle.
    *Gall. 1930 (per Wgt.3):
    The weaver's homespun tweed was usually of a natural or hoddin grey colour, or amber when dyed with crottle.

    3. Combs.: (1) black crottles, the lichen Parmelia saxatilis (Sc. (Highlands) 1886 B. and H. 130); (2) crottal-coatie, ``a brown coat or jacket dyed with `crottal''' (Ags.17 1941); (3) crotal-colour, pale brown; (4) light crottles, the lichen Lecanora pallescens (Sc. 1886 B. and H. 130); (5) stone crottles, = (1) (n.Ir. Ib. 131).
    (3) *Arg. 1901 N. Munro Doom Castle iii.:
    Now the tartan's in the dye-pot, and you'll see about here but crotal-colour --- the old stuff stained with lichen from the rock.

    [Gael. crotal, a gen. name for the varieties of lichen, more especially those used in dyeing (Macleod and Dewar).]