They stood Englishly around a bandy-legged Scot with a thrummy beard.Guy Davenport, "A Field of Snow on a Slope of the Rosenberg," Da Vinci's Bicycle, 1979
... And on her head a thrummy cap she had.John Chalkhill, Thealma and Clearchus: A Pastoral Romance, 1683
Origin of thrummy
Thrummy is formed from the noun thrum meaning "one of the ends of the warp threads in a loom, left unwoven and remaining attached to the loom when the web is cut off." It entered English in the late 1500s.