Ail
Old English eglian, eglan, from egle ‘troublesome’, of Germanic origin; related to Gothic agls ‘disgraceful’.
wiktionary
From Middle English eilen, from Old English eġlan, eġlian(“to trouble, afflict”), cognate with Gothic 𐌰𐌲𐌻𐌾𐌰𐌽( agljan, “to distress”).
From Middle English eyle, eile, from Old English eġle(“hideous, loathsome, hateful, horrid, troublesome, grievous, painful”). Cognate with Gothic 𐌰𐌲𐌻𐌿𐍃( aglus, “hard, difficult”).
From Middle English eile, eyle, eiȝle, from Old English eġl(“an ail; awn; beard of barley; mote”), from Proto-Germanic *agilō(“awn”). Cognate with German Achel, Egel, Ägel.
etymonline
ail (v.)
c. 1300, 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.
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]
