The FBI Created Their Own Motto as a Backronym
It's strange that the FBI now uses a backronym in its name since the organization is already an acronym. The Bureau of Investigation was the name of the organization when it was founded back in 1908. It changed its name to the Federal Bureau of Investigation in 1932 after first becoming the United States Bureau of Investigation.
The FBI is primarily known by its initials, like many other agencies like the CIA, NSA, or DOD, although its entire name is simple enough to recall and use verbally if necessary. However, they also adopted a slogan that was printed on their official seal when they accepted the name in 1935. But when they took on their official name in 1935, they also acquired the motto "fidelity, bravery, and integrity," which was printed on their official seal.
At the time, the bureau of inquiry portion of their name was already close to 30 years old. The decision to adopt a motto, while admirable, now looks a little performative because it was tacked onto their initials as a backronym after the name had already been chosen.