Omicron is a letter I’ve used so rarely that I don’t know how to pronounce it. Other Greek letters I’ve come across in sciencey stuff, but not omicron. And it wasn’t until this morning that I realised omicron is little O and omega is big O. Anyway, Greek letters make it sound as if the experts know what they are doing – which one the whole, as far as it can be known, the do. Also since it’s a world thing, Latin letters might be inappropriate.