thrum cap
Webster's Dictionary (GCIDE)
Thrum \Thrum\ (thr[u^]m), n. [OE. thrum, throm; akin to OD. drom, D. dreum, G. trumm, lump, end, fragment, OHG. drum end, Icel. [thorn]r["o]mr edge, brim, and L. terminus a limit, term. Cf. Term.] [Written also thrumb.]
1.One of the ends of weaver's threads; hence, any soft, short threads or tufts resembling these. [1913 Webster]
2.Any coarse yarn; an unraveled strand of rope. [1913 Webster]
3.(Bot.) A threadlike part of a flower; a stamen. [1913 Webster]
4.(Mining) A shove out of place; a small displacement or fault along a seam. [1913 Webster]
5.(Naut.) A mat made of canvas and tufts of yarn. [1913 Webster]
Thrum cap, a knitted cap. --Halliwell.
Thrum hat, a hat made of coarse woolen cloth. --Minsheu. [1913 Webster]