foolish, idiotic, or simple-minded ...1735
a witless or stupid person, a blockhead ...1668
from lack (vb.) + wit
First Documented Use: 1668
"Faith, sir, my skill is too little to praise you as your deserve; but if you would have it according to my poor ability, you're one that had a knock in your cradle, a conceited lack-wit, a designing Ass, a hair-brain'd fop, a confounded busie-brain, with an eternal windmill in it..."
From: Sr Martin Mar-all; or, The Feign’d Innocence
- John Dryden