from the GNU version of the Collaborative International Dictionary of English
- n. the Monday after Twelth Day, or the end of Christmas holidays.
from The Century Dictionary and Cyclopedia
- n. The Monday after Twelfth-day, or the termination of the Christmas holidays, when the labors of the plow usually began, observed in England as a rustic festival. On that day it is the custom of plowmen to draw a plow from door to door, soliciting drinkmoney. Also called Rock Monday.
Sorry, no etymologies found.