When I was younger, I always thought that a ten gallon hat would actually hold ten gallons of water. Then, later, I realized that for a ten gallon hat to hold ten gallons of water, it would have to be much larger than they are. My life was changed forever.
Then at breakfast yesterday I noticed that the pots we buy marked as one gallon pots are not one gallon, but about three quarts. Neither are our five gallon pots equal to five gallons. It seems this happens a lot. For instance, boards marked as 2 x 4 are not actually 2 x 4.
I read in a couple of places that the reason for the pots being misnamed is that nurseries and other places that sold them called the pots #1 pots, #2 pots, #3 pots, and so on. These sources stated that some people just started calling them 1 gallon pots, 2 gallon pots, and so on, even though they didn’t hold those amounts at all. I don’t know if that’s true, but it certainly seems like a reasonable explanation.
If anyone knows how this actually got started, feel free to educate us!