Why is the song called that
The original was ハダカのキモチ (hadaka no kimochi). Going backwards:
"Kimochi" means feeling.
The "no" is just connecting the two words.
And so we get to "hadaka". It
can mean nude/naked/without clothes, which would give you the "feeling of being naked"[1]. But it can also have a meaning of "concealing nothing", which would give you something like "completely honest feelings".
Maybe "Naked feelings" would've been better?
[1] - Google says there's a brand of underwear that uses "hadaka no kimochi" as a slogan, probably with this meaning.