ETYMOLOGY
from smart (sharp physical pain) + -ful
EXAMPLE
“…What kind harted husband: can se his kind wife,
In like carefull case, without wo at his hart.
What naturall father can se: for his life,
His naturall childerne, in dread quake and start.
Without his hart smarting, in most smartfull smart.
I thinke, ye thinke none: and euin so thinke I.
Meruell not then: though the spider be toucht nie…”
From: The Spider and the Flie
By John Heywood, 1556
Lexicophilia 