I was working on a piece of kit for password hashing the other day and realised that I didn't really known what the term endianism refers to. So I looked it up.
I was pleasantly surprised to find that the term, which is now an IT term more than anything, harks back to the story of Gulliver's travels.
In short, endianism refers to the order in which bytes are stored; whether the "big end" is to the left or to the right. Big-endian stores the "big-end" to the "left" (or first), and Little-endian stores the "big-end" to the right (or last). You can read a pretty good explanation of it here, and if you're interested in Jonathan Swift and how he originated the term you can read about that here.