c.1300, Scottish and northern English variant of loathly "hideous, repulsive" (see loath).
Online Etymology Dictionary, © 2010 Douglas Harper
Examples from the Web for laidly
The peasants are in deep distress The laidly bear should them oppress.The Dalby Bear
"I have only a—a parcel," Barrie meekly confessed, feeling three times a worm, even a Laidly Worm.The Heather-Moon
C. N. Williamson and A. M. Williamson
All was done as the warlock advised, the Laidly Worm lived on the milk of the seven kine, and the country was troubled no longer.English Fairy Tales