Google Book Search tells me that these words appear in a book called "Frontier Ballads" by Charles Joseph Finger, 1927, page 115:

Chorus: For it's gently, softly, slowly does the trick,
You'd walk clanky, ...

-and-

Chorus: Come down softly, gently, easy does the trick,
Just fall easy, careful, never be too quick,
Your eye the distance gauges
So you land by easy stages ...

[I suggest you click the link above and then click "Find this book in a library."]