What does "plus ultra" mean in My Hero Academia The credits for My Hero Academia add "plus Ultra" after the series name.  Occasionally All Might shouts "plus Ultra!" as sort of a battle cry when he is about to strike a foe.  From context, I guess it means "extra power" or "boost", but "plus ultra" seem so random. Is there more meaning to the two words than this? Is this just something which does not translate well from Japanese?
"Plus Ultra" is actually a Latin Phrase. It translates to "Further Beyond." In My Hero Academia, it has been adopted as the school motto of U.A. High. It's uncertain in-universe whether or not the motto was around before All Might, or if he's the one who came up with it, and his alma mater adopted his personal motto.

In-context, it is an extremely gung-ho statement that tells you to push past your limits and go further than you think you can.

It also happens to be the national motto of Spain, previously the personal motto of King Charles V. Which he adopted as a rejection of the words inscribed on the Pillars of Hercules "Non Plus Ultra" (Nothing Further Beyond) after the discovery of the Americas.

Even IRL, it carries that same sort of gung-ho "You told us there was nothing beyond this point...let me prove you wrong!" sort of sentiment.

The fact that it sounds cool to Japanese Ears by using a pair of English-adopted words that they like is bonus points. But this phrase is not, in-fact, "English" gibberish as anime/manga occasionally produces on account of their writers not being entirely fluent in English. It's a Latin phrase with real-world history.