According to both Google Trends and my observations of the world, the word emoticon has been decreasing in usage of late, in favor of emoji. Both describe a small digital picture often used on the Internet, and both sound similar, but the roots are different, etymologically speaking. Additionally, a schism in definition caused "emoticon" to mainly mean characters created out of text, and "emoji" to be ready-made images. Emoticon, which was coined by 1994, is a portmanteau of the words emotion and icon, which is pretty self-explanatory. Emoji is much cleverer. Shigetaka Kurita, the man who invented the modern pictorial variation, named them that as a sort of play on words: it sounded like both emoticon and kanji, a Japanese system of writing, but actually combined the words e, meaning "picture", and moji, meaning "character". Best pun since Shakespeare, in my opinion. E is very simple and therefore has a very simple etymology. It probably comes from a Chinese word meaning "drawing" and sounding like huay, which always sounded like that and meant that. Moji, meanwhile, is thought to be from Middle Chinese midzi, meaning "writing-character", also without much change before that. So an emoji carries the hidden meaning of "drawing-writing-character"!
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.