Meaning
What does Bnha mean?
Origin
What's the origin of Bnha?
The manga series started out in 2014, and is still ongoing, while the anime series started out in 2016. Shortly after the brand’s debut, fans started to refer to it with its acronymic name, maintaining secrecy and avoiding a possible mispronunciation and the repercussions coming with it.
Spread & Usage
How did Bnha spread?
Both the manga and the anime series gained great popularity and very good ratings, shortly after their release, with weebs flocking onto one more good anime to watch and one more good manga to read.
The first Urban Dictionary entry of Boku No Hero Academia was added in 2018, mocking people who call the series that way.

External resources
- Fandom – My Hero Academia Wiki