ail (v.)

Middle English eilen, ailen, "trouble, afflict, harm," from Old English eglan "to trouble, plague, afflict," from Proto-Germanic *azljaz (source also of Old English egle "hideous, loathsome, troublesome, painful;" Gothic agls "shameful, disgraceful," agliþa "distress, affliction, hardship," us-agljan "to oppress, afflict"), from PIE *agh-lo-, suffixed form of root *agh- (1) "to be depressed, be afraid." Related: Ailed; ailing; ails.

From late Old English also of mental states and moods. Phrase what ails you? "what is wrong with you? why do you behave that way?" is by c. 1300 (what eileth the?)

It is remarkable, that this word is never used but with some indefinite term, or the word no thing; as What ails him? ... Thus we never say, a fever ails him. [Johnson]

updated on September 16, 2022

Definitions of ail from WordNet
ail (v.)
be ill or unwell;
ail (v.)
cause bodily suffering to and make sick or indisposed;
Synonyms: trouble / pain
ail (n.)
aromatic bulb used as seasoning;
Synonyms: garlic
Etymologies are not definitions. From, not affiliated with etymonline.