There are many hits for this phrase. Some of them are indeed fragments of this song. None, that I can find, tells me about a complete song with this title.
It looks like a fragment that has become attached to the college version parody of "Minnie the Mermaid". But -- It sure sounds like a different song and I can't help thinking that it once was. The whole Mermaid idea seems to get lost in the second half.

Here's how True-love learned it in the 1950s - in America.
(Some versions have minor word differences and/or changes to the line-order in the second part.)

Minnie the Mermaid - parody version

Oh, what a time I had with Minnie the Mermaid,
Down at the bottom of the sea;
Down among the corals, Minnie lost her morals
Gee but she was good to me.
Many's the night beneath the pale moonlight,
In her seaweed bungalow,
Ashes to ashes, dust to dust
Two twin beds only one was mussed.

Well, you can easily see she's not my sister,
'Cause my sister's too refined
And you can easily see she's not my sweetheart,
'Cause I never showed my sweetie such a helluva good time.
Well, you can easily see she's not my mother,
'Cause my mother's 49.
She's just an innocent kid
She never cared what she did;
She's a personal friend of mine
(She does my laundry), a personal friend of mine.

Puzzled. Can anyone shed any light?
Cheers, Joy