Heavens to Betsy
A mild exclamation of surprise.
This American phrase has been in circulation since, primarily restricted to America, the latter part of the 19th century, although its use faded throughout the 20th century and it is now something of an anachronism. The first example of it that I can find is from the US journal Ballou's dollar monthly magazine, Volume 5, January 1857:
Heavens to Betsy!" he exclaims...
It is possible that the phrase is a minced oath and an alternative to 'Hell's bells', although there's no real evidence of that,
Of course, what we would like to know is, 'was Betsy a real person and, if so, who?'. Various theories have been put forward. The most common of these is that Betsy was Betsy Ross, who stitched the first American flag. Another is that the Betsy referred to is the slang name that early US settlers used for their favourite pistol or rifle. Neither of these theories comes accompanied by any evidence and, as always, speculation must be put into etymological limbo. It is unlikely that she will be identified.
For phrases that contain names that are genuinely eponymous, that is, named after a known person or fictional character, it isn't difficult to trace the person concerned, as in 'sweet Fanny Adams', 'kiss me Hardy' etc. When we come to phrase like 'Mickey Finn', 'happy as Larry', where there is doubt as to the named person, a strong case can be made to suggest that the names were invented. That seems to be the case with Betsy.
The etymologist Charles Earle Funk published Heavens to Betsy! and other curious sayings in 1955. In that he ventured the opinion that the origins of 'Heavens to Betsy' were "completely unsolvable".
See also: Heavens to Murgatroyd.