In addition to it's origins.
To happen upon-
To accomplish or benefit from a situation with little or no effort -
To have something of good or bad fortune happen out of the blue- or without expectation-
Void of expectation
On the humbug, I went into McDonald to get some napkins, because my kid fell and scraped her knee. Where I ran into my old girl friend, I had not seen or talk to in more than ten years. She happened to be a doctor now, and helped me clean and inspect her knee.
On the humbug, I got a raise at work today!
My girl gave me some good loving today on the humbug.
My friend stopped by my house today on the humbug.