What does this idiom mean: "I've got you under my skin"? (Frank Sinatra

[Olga!]

Test No. express/inter-10 "Under my Skin", question 6

He looked at her and in the words of Frank Sinatra said: 'I've got you under my skin'.

(a) I'm very pleased with you
(b) I'm very proud of you
(c) I'm very attracted to you
(d) I'm very surprised by you

Test No. express/inter-10 "Under my Skin", answer 6

He looked at her and in the words of Frank Sinatra said: 'I'm very attracted to you'.

Correct answer: (c) I'm very attracted to you
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Can you explain answer on my question?
What does mean aspect "I've got you under my skin"?

[Guest]

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It is an idiomatic expression for very attracted to/very used to/unable to stop thinking about.

To have a splinter or a tattoo under one's skin is to have it indelibly lodged with you.

In addition, to get under one's skin is to irritate one:

My boss really gets under my skin-- he's always looking over my shoulder.
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