The term is what Navy basic training is referred to. Actually all services refer to basic training as boot camp. The term comes from the leggings worn by new recruits during the time of the Spanish American War. The leggings are worn to give extra support to the ankles and to keep dirt our of the persons boots.

The leggings at this time were made from a thick canvass material. They ran from the boot up to the top of the calf and buckled up the back. This gave the appearance of the person wearing a large boot. So the recruits wearing the leggings were soon called boots and then of course the camp they were trained in became boot camp.

Sometimes fact is stranger than fiction. But in this case a simple explanation.

I have many stories from boot camp, some short, others long. We wore leggings a good deal of time when we matched. They do keep your ankle snug but are very hot! They are also a major pain to keep nice and clean.