Whether to sound out an acronym one letter or a time or try to make it a word. It is something I talked about previously in How is that pronounced, exactly?.

Though I doubt anyone can reliably track down the original sources of the SQL pronunciation as ESS-QUE-ELL vs. SEQUEL, MUI gives us a better chance to figure out what happened here.

In the beginning, it was called EM-YOU-EYE (MUI).

And it h