Above: Detail of a column from Canterbury Cathedral crypt, showing a devil playing a croud.
also crowth, crouth (Medieval English), crwth (Welsh), cruit (Gaelic) crot, cruit (Irish)
'....An ancient plucked and bowed stringed instrument which had more or less rectangular frame the lower half of which was filled in as a sound-box, with flat (or occasionally vaulted) back, the upper half being left open on each side of the strings.' Oxford Companion to Music
'... An ancient Celtic six stringed violin, four of the strings being bowed and two struck by the thumb in playing ...' Webster Dictionary 1904
The origins of the surname are to be found in a person or family who were known for playing the croud, a medieval stringed instrument.