It is archeic scottish.
It means a spell, charm, or trick.
Sc. 1725 Ramsay Gentle Shepherd Act II. Sc. ii. in Poems (1728):
Here Mausy lives, a Witch, that for sma' Price Can cast her Cantraips, and ...
Dagon's Maw, or the Pit of Hatred
Some SPOILERS follow for the Tammeraut's Fate adventure (in 3.5e version and also a part of the 5e Ghosts of Saltmarsh book).
The module Tammeraut's Fate from Dungeon ...