Not sure how accurate these lyrics are.
Found them here

Excuse the line breaks (or lack of them)


There was a time when sex seemed something quite complex.
Mister Freud then employed words we never had heard of.
He kept us on the string.
We kept on wondering.
But the seed of sin now at last has been found by Eleanor Glynn.
In one word she defines the indefinable thing.
She calls it "it".
Just simply "it".
THat is the word they're using now for that improper fraction of vague attraction that gets the action somehow.
You've either got (or you have not) that certain thing that make's 'em cling.
SO if the boys don't seem to fall for you,
there's just no hope at all for you.
Give up and quit.
YOu'll never hit.
If you have not got "It".