is the Old English adela (filth), hence rotten, putrid, worthless.
A worthless egg. An egg which has not the vital principle.
Addle-headed, addle-pate, empty headed
As an addle-egg produces no living bird, so an addle-pate lack brains.
(The) Addle Parliament (The)
5th April to 7th June, 1614. So called because it did not pass one single measure. (See Parliament.)