ETYMOLOGY
from sleight (adroitness, nimbleness of mind or body) + -ful
EXAMPLE
“…Not worschipe men for here worldly rychesse. as þe fals world doþ
for þey be mysdoers, sotel, and slyhtful dysseyuers…”
From: The Lay Folks’ Catechism
(Lambeth MS.). 1380
Lexicophilia 