Unfortunately, dictionaries are sadly lacking. Here's what I googled up this morning about crwth, after having come up with nada in any of the OneLook references, including the illustrious Mr. Fischer's:

Crwth is a generic term denoting several small lyres that flourished in western Britain from the eleventh through early nineteenth centuries. Neither crwth nor its many cognates, partial-cognates, and synonyms necessarily indicate any one particular instrument. Specific denotation depended on time, exact locale, and, in some instances, specific individual. Hence written references to performance must be evaluated with care.

The modern crwth was one of the last of the European bowed yoke lyres. Rather than evolving along a single line in the manner of the viol and violin,, the bowed yoke lyre repeatedly split into varied designs, due in great measure to its having been subjected to much experimentation, structural variance, and disparity of playing technique.

http://home.earthlink.net/~llywarch/cth03.html

Brings whole new meaning and depth (crwth as instrument and also as crowd) to that ol' dark fiddler's novel, Far From the Maddening Crwth, huh?

Best regards,
DiddleDub, whose gray matter insisted she was correct!