A friend who listens to the Lexicon Valley podcast shared this incredibly satisfying bit of info.
The Greek letters Omicron and Omega are two versions of the letter O: the short vowel sound (o as in obsolete) and the long (o as in OMG).
The words mean “O – micron” for the short sound – really short, like a micron – and “O – mega” for the long sound. Mega long.
If those words were in English, Omega would be pronounced “ah-mega” with the short sound. Because why? Because English makes no sense ever since France came in and imposed their own rules and now they insist on cultural purity for French after cluttering up English.