DCHP-1 Online
thrum-cap [< thrum cap a cap of cloth embroidered with thrums (waste ends of the warp); see 1958 quote] Esp. Atlantic Provinces, Obs. (except in place names) 
n. a small island, especially one having a conical appearance with a tuft of trees in the centre; also a shoal of similar shape.
- 1832 Opposite to this point an islet or thrum-cap, (as these are termed), was once considered available for the purpose of drawing fish. . . .
- 1832 Another thrum-cap island contiguous to the above is of no value whatever.
- 1934 And on the outer Thrum Cap shoal he ran her hard aground.
- 1958 The toponymic frequency of thrumcap is due to the ubiquity of a type of headgear [worn] among sailors of the Maine and Canadian coasts a century and a half ago and the presence of certain islands resembling it in shape and appearance.
- 1832 Opposite to this point an islet or thrum-cap, (as these are termed), was once considered available for the purpose of drawing fish. . . .