This really bugs me, even though I know it's inconsequential · 7:34am Jul 22nd, 2015
Remember Tantabus? Good old Tantabus created by Luna to punish her for the whole Nightmare Moon thing?
So, the word apparently comes from "tantibus" which is allegedly Latin for "nightmare". I say "allegedly" because despite trying quite hard, I have not been able to actually find a reputable source that confirms there even is a Latin word such as "tantibus".
And, no, Google Translate is no reputable source.