addle
UK[ˈæd.l̩]US[ˈæd.l̩]
v
To make or become confused or muddled.
adj
(of an egg) Rotten or bad, producing no chick.
Etymology
The word 'addle' originates from the Old English term 'adela', meaning liquid filth or mire, a stinking, putrid substance. This sense of foul, confused matter evolved metaphorically by the 17th century to describe a confused or muddled state of mind, as if one's thoughts were in a figurative mire. The specific application to rotten eggs, where the clear white becomes a muddy, foul-smelling liquid, directly preserves the original concrete meaning of corrupted fluid. Thus, the word's journey connects physical corruption and foulness to abstract mental confusion.
Analysis
This is a simplex word of Old English origin. The modern form is a result of phonological fusion and semantic narrowing from its original state.
Examples
The constant noise began to addle his brain.
We discovered an addle egg in the nest.
Too many conflicting instructions will only addle the new trainees.