also 'pon, 1550s, shortened form of upon.
Examples from the Web for pon
I'm blessed if I don't think—'pon my life, I believe we've met before!Ten Thousand a-Year. Volume 1.|Samuel Warren
"'Pon honor, my dear fellow, I don't know," replied Lord Algernon.Quincy Adams Sawyer and Mason's Corner Folks|Charles Felton Pidgin
All these stories began "Once 'pon a time," but each one ended differently.The Child's Book of American Biography|Mary Stoyell Stimpson
"'Pon my honour, though, that man must be off his dot," and the lady in blue went into convulsions of hysterical giggling.The Christian|Hall Caine
"'Pon my honour and word, it's true, though," said old Frot.The Mysteries of Paris, Volume 4 of 6|Eugne Sue