The in-universe publisher of "Fantastic Beasts and Where to Find Them" is called Obscurus Books, as shown on the title page. It's also referred to in the foreword by Albus Dumbledore.
“For the first time in the history of the noble publishing house of Obscurus, one of its titles is to be made available to Muggles.” - Albus Dumbledore, Fantastic Beasts and Where to Find Them
Then it's named again in the introduction by Newt Scamander.
“The first edition of Fantastic Beasts was commissioned back in 1918 by Mr. Augustus Worme of Obscurus Books, who was kind enough to ask me whether I would consider writing an authoritative compendium of magical creatures for his publishing house.” - Newt Scamander, Fantastic Beasts and Where to Find Them
In the "Fantastic Beasts and Where to Find Them" movie, something called an Obscurus has a big role in the events that take place.
An Obscurus is a dangerous dark force created by a child who knowingly represses their magic, which causes destruction and chaos then eventually leads to its host dying.
It's too big of a coincidence for the name of the Obscurus being the same as the publisher of the original textbook to not be intentional, and considering that the movie and textbook are so strongly interconnected, presumably there must also be a reason for the publisher being named after the Obscurus seen in the movie.
Why, in-universe, would a publisher choose to be named after a force like the Obscurus?