The ones we hear about are the variants of concern ie Omicron, Delta. There were other variants too, such Lambda and Mu which are variants of interest only. I guess they are on the watch list but never took off.
They missed out nu because of it’s obvious similarity to new And xi because it’s a common Chinese surname. That doesn’t account for the other missing letters though…
Thanks Fanny, that explains why we have never heard anything about the ten missing letters. Makes you wonder why they started using the alphabet if they were not going to same the variant sequentially.
I heard the explanation a while ago; but don’t remember the details. They missed out various letters because they sound like other things in other languages, including the Chinese president (I think). Basically, it’s just for global clarity,