You’ve probably come across a lot of English idioms. Some of them don’t seem to make much sense at all, like saying that it’s raining cats and dogs. Other idioms can almost be taken literally, like talking about winning by a hair’s breadth. These idioms become particularly challenging when the words used are oftentimes only seen or heard in the context of that specific idiom.
A prime example of this is when you talk about hitting the mother lode. Or is the mother load?
As far as I know, this is an idiom that is largely only used in American English, though I’m sure it has spread to English variations in other parts of the world too. The correct spelling is mother lode, even though a mother load might almost make sense. It also doesn’t help, as mentioned, that the word “lode” isn’t really a part of our normal, everyday speech.
Most of us are likely familiar with the word load. Used as a noun, it would refer to something large or heavy that is going to be carried in one go. The wall shelf can carry a load of up to 20 pounds. It could also refer to the pressure taken on by something that is carrying that added weight. The engine could not handle the extra load. If you want someone to relax or to relieve themselves of a burden, you might tell them to take a load off. “Load” can also be used as a verb. When you open a file on your computer, you’re also “loading” that file.
A lode is a different word altogether. In a geological sense, a “lode” refers to a deposit of ore or a mineral (usually valuable) found in the crack or space in a rock formation. If some gold is filling a crack in the side of a cliff, then you could say that there is a lode of gold in there. You might also hear people talking about the mineral lodes at a mine site. Given this, a “lode” can be generalized to refer to an abundant supply of non-minerals too.
In a literal sense, then, a mother lode is “a principal vein… of gold or silver ore.” In a more figurative sense, a mother lode can refer to a large stash of something valuable and that’s why the idiomatic phrase makes sense. Whether you’re talking about a valuable treasure, a room filled with guns, or a library filled with great knowledge, you could be hitting a mother lode.
I’ll admit that I always thought it was mother load too. Then again, outside of some obscure video game references, I’ve hardly ever come across the word “lode” at all. Go figure.