nagel i ögat

Etymology
Compound of.

From the Bible quote Numbers 33:55, "But if ye will not drive out the inhabitants of the land from before you; then it shall come to pass, that those which ye let remain of them shall be pricks in your eyes, and thorns in your sides, and shall vex you in the land wherein ye dwell.".

Today's use of the synonymous idiom is most likely due to the relative unfamiliarity with the arachic meaning of, which today often refers to a finger nail.

Noun

 * 1)  A source of irritation, chagrin, vexation or annoyance.