Probably no one knows this song, but anyways...

"Eighteen years with you" secretly sung by Gwydion at Manannan.
To the tune of "Sixteenth Century Man" by Elton John from the El Dorado soundtrack.
Oh it'd be great to see my homeland
Live where you I don’t have to hear
Just because I am compliant
Doesn't mean I’m not defiant
Quite frankly I’ve had water up to here
I've made meals to last a lifetime
I've been so scarred, almost killed
I’m intelligent, not half-witted
I’m determined, not uncommitted
I'll seek my fortunes once your heart is stilled
There's no future to be found here
No one would believe the tales
Of me growing much older
Which I won’t, if this plan fails
I have seen the way the tide is turning
My time is almost through
I am on the ball, discerning
And thus my plan grew
I’ll take my leave after
Eighteen years with you
I’ll take my leave after
Eighteen, Eighteen years with you
One evening while you’re dining
A special something will cut it short
Now at last I’ll get my sweet revenge
For all the past wrongs, I will avenge
I have reached my final and last resort
There's no promise in your old words
It's a trick to keep me down
While you’re gone and busy,
I’ll take a trip to town
I’m going back to where I came from
Never mind I don’t know where
All in all the point I've made is
I don't want to stick around
I’ll take my leave after
Eighteen years with you
I’ll take my leave after
Eighteen, Eighteen years with you