The word and constitutes just under 2.4% of all words used in the English language, although usage has decreased since its peak around 3.2% in the 1650s. According to my extensive collection of Zipf's Law graphics, it's the third most common word in the English language. Now, if we look at the etymology of and, we can see very little variation in both definition and spelling. This is unsurprising, as it is a fundamental word- so basic that there's not much to change. It's been around that long. In Old English, more than a thousand years ago, it was still a conjunction meaning "and", but if we go a quarter millennium back to Proto-Germanic, it was either unda or andi, depending on the reconstruction. Even further, in Proto-Indo-European, it actually had a different definition, that of "in", as the word en. Why? Not sure. It's tentative at best.
Adam Aleksic, a rising sophomore studying linguistics and government at Harvard University, has been described as the internet's sixth most famous etymologist. He also has disturbing interests in politics, vexillology, geography, board games, conlanging, and law.