User blog comment:Kir the Wizard/Thawne's Deadline – The Black Flash!/@comment-7890302-20170109161534/@comment-24152851-20170116104752

Eobard was called Zoom outside the comics as well. When he appeared on Batman: Brave and the Bold, voiced by our living legend John Wesley Shipp, he was just called "Zoom" rather than "Professor Zoom".

He's officially Professor Zoom to differentiate him from Hunter's Zoom, but that doesn't stop plenty of characters to call Eobard "Zoom" for short.

The Reverse-Flash was actually the name for most of the Flashes arch-enemies, rather than only Eobard. But Arrowverse decided to make Eobard the sole owner of that title, probably because "Professor Zoom" was too cheesy or it'd get confusing with the other Zoom.