In English at least, the corresponding Greek letter is normally spelled "upsilon", which is obviously similar. The "psilon" in both "upsilon" and "epsilon" mean

In English at least, the corresponding Greek letter is normally spelled "upsilon", which is obviously similar. The "psilon" in both "upsilon" and "epsilon" meant somethign like "simple" in Greek. So these letters were the "simple u" and "simple e". (Similarly with "omicron" and "omega", you can probably guess what size of "o" those were. :) Not sure if there are other cool facts about the Greek letters, for example those ending with "eta".