Meaning of 801
801 means love (story) between boys.
Pronunciation of 801 is Yaoi.
The meaning of this is almost same with BL but 801(yaoi) is an obsolete word I think.
By the way, Japanese read numbers in various pronunciation,
so if you are interested in it, check this 893
A: I used to like 801.
B: What’s the 801?
A: Today’s BL.