An ailment; trouble; illness.
The awn of barley or other types of corn.
be ill or unwell
To cause to suffer; to trouble, afflict. (Now chiefly in interrogative or indefinite constructions.)
Painful; troublesome.
The word "ail" comes from Old English, where it originally meant to trouble or afflict. Its roots trace back to Proto-Germanic and are related to the Gothic word for distress.