Grandma and Grandpa might seem awfully buttoned-up, but back in the day they could curse like crazy, too. The thing is, they used different words and phrases, all of which seem tame by today's standards, but at the time probably infuriated their parents and grandparents with their saucy nature.
1. Son of a Gun
It's pretty hard to definitively know where any type of slang originated, so it's no surprise that etymologists disagree over how "son of a gun" came to be. It could be as simple as a milder take on "son of a bitch," which has been said for centuries in reference to fatherless children. The phrase can be used in a number of situations appropriately, whether out of anger, joy or bewilderment ("Son of a gun, that old Model-T still starts after all these years!")
Another possible origin is that it actually means "son of a military man." The British Navy, in particular, allowed women (wives, prostitutes, what have you) on sailing vessels, and as a result, children were occasionally born on board. So, on the birth certificate the child's father (if paternity was uncertain) would be listed as "son of a gun," translated to "son of a military man." Even if the baby was a girl. Go figure.
Call it what you will – dadgummit, dagnabbit or goldarnit, these alterna-swear words are simply ways your grandparents got around breaking any biblical commandments against "taking the Lord's name in vain" outright. Replace the first part with "God" and the second part with "damnit," and you get the picture easily enough.
The origin of "dadgummit" is rumored to be the hit television show "The Real McCoys," which starred Walter Brennan as Grandpa Amos, for whom "dadgummit" became his epic, country-boy, redneck catchphrase.
Our grandparents really thought they were getting away with swearing with this phrase, but we're all bright enough to know that H-E-double-hockey-sticks is just another way to say "Hell." No knows who the H-E-double-hockey-sticks came up with this euphemism first.
4. Sam Hill
Ever wondered who Sam Hill was and what he did so wrong to have elders yelling out his name all the time ("What in the Sam Hill are you talking about, boy?"). Well, many Sam Hills have existed, but none of them spawned the old saying, which is simply another way of saying "Hell" without actually saying it. It dates to the early 19th century.
Now, here's another old-timey phrase you'd hear on TV Westerns. The word "tarnation," which dates back to the 18th century, comes from "darnation" which is derived from "damnation." It's also associated with another "curse word," "tarnal," which is a form of "eternal." As the Word Detective, put it, "To speak of 'the Eternal' at that time was often to invoke a religious context (God, Heaven, etc.), and thus to label something or someone 'eternal' in a disparaging sense ('You eternal villain!') was considered a mild oath."