it was originally formed from "I shall warrant" and later taken as a mincing substitute for "I swear".
Mincing...I love it! "I shall warrant"--Wow, just like good-bye! Cool! Thanks, O non-mincing one.
I've heard I'll swan and I'll swanee all my life.

Helen, is "The Coalwood Way" as good as October Sky/Rocket Boys? I've thought about reading it.