ail

Etymology 1

From Middle English eilen, from Old English eġlan, eġlian (“to trouble, afflict”), from Proto-West Germanic *aglijan, from Proto-Germanic *aglijaną (“to trouble, vex”), cognate with Gothic 𐌰𐌲𐌻𐌾𐌰𐌽 (agljan, “to distress”).

verb

1. (transitive) To cause to suffer; to trouble, afflict. (Now chiefly in interrogative or indefinite constructions.)
   Have some chicken soup. It's good for what ails you.
   Not content with having in 1996 put a Defence of Marriage Act (DOMA) on the statue book, Congress has now begun to hold hearings on a Respect for Marriage Act. Defended, respected: what could possibly ail marriage in America? 2011, “Connubial bliss in America”, in The Economist
2. (intransitive) To be ill; to suffer; to be troubled.
   When he ails ever so little […] he is so peevish. 1740, Samuel Richardson, Pamela; or, Virtue Rewarded

noun

1. (obsolete) An ailment; trouble; illness.

Etymology 2

From Middle English eyle, eile, from Old English eġle (“hideous, loathsome, hateful, horrid, troublesome, grievous, painful”). Cognate with Gothic 𐌰𐌲𐌻𐌿𐍃 (aglus, “hard, difficult”).

adj

1. (obsolete) Painful; troublesome.

Etymology 3

From Middle English eile, eyle, eiȝle, from Old English eġl (“an ail; awn; beard of barley; mote”), from Proto-Germanic *agilō (“awn”), related to *ahaz (“ear (of grain)”). Cognate with German Achel, Egel, Ägel.

noun

1. The awn of barley or other types of corn.