Here's a 1999 recording by Bev Bos. The lyrics are just a bit different from those posted above.
https://www.youtube.com/watch?v=go_4oepb3io

ONCE A GIANT CAME A-WANDERING

Once a giant came a-wandering
Late at night when the world was still
Looking for a stool to sit on
He climbed a little green hill.

Finally he reached the highest part of it
Sat himself down on the very peak
Then he heard the hill cry out
In a faint and faraway squeak:

Giant, giant, I am under you
Move or this is the last of me
But the giant said, no, thank you
I like it here, don't you see.