Other forms: addled
To addle is to muddle somebody's thinking. Addle your brain, addled with drink, addle the mind.
It survives mainly as addled and in addle-brained. An addled egg is one that has gone rotten, which is the original sense — the Old English word meant liquid filth, and an addled egg is one that never developed. The thinking sense came from that rottenness.
1verbaddleTo muddle somebody's thinking.
“The long night shift had addled his brain, and he kept forgetting simple words.”
addle is a muddling.
Also accepted in games: befuddle
Middle English adel means rotten, from Old English adela, filth or liquid manure. An addled egg was a rotten one.
Proto-Germanic
*adalaz
Proto-West Germanic
*adal
Old English
adela — mire, pool, liquid excrement
Middle English
adel — rotten
English, today
addle
Built from
From Middle English adel (“rotten”), from Old English adela (“mire, pool, liquid excrement”), from Proto-West Germanic adal, from Proto-Germanic adalaz, adalô (“cattle urine, liquid manure”). Akin to Scots adill, North Frisian ethel (“urine”), stq adel (“dung”), Middle Low German adele (“mud, liquid manure”) (Dutch aal (“liquid manure”)), Old Swedish adel (“urine”), Danish ajle (“liquid manure”), Bavarian Adel (“liquid manure”).
Etymology from Wiktionary, CC BY-SA