ZBLL
Petrus was the original 3x3 speedsolving method that reduced to an all edges oriented last layer.
See the Petrus method page.
Bernard Helmstetter generated all of the algorithms for the Petrus method to solve the last layer in a single step in 2000 - 2001.
Lars Petrus states that Helmstetter's algorithms would be a great way to exploit the Petrus method's advantage of having all last layer edges already oriented.
This message is from the SpeedSolvingRubiksCube Yahoo group.
Lars Petrus has Helmstetter's work mentioned on his website.
Zbigniew Zborowski and Ron van Bruchem proposed the idea of orienting the last layer edges during the last pair in the CFOP method in 2001.
This message is from the SpeedSolvingRubiksCube Yahoo group.
Zbigniew Zborowski states on his website for ZBLS to use Helmstetter's Petrus method algorithms for the last layer.
Helmstetter's algorithms were added to Speedcubing.com, a site owned by Ron van Bruchem.
Website for ZBLS.
The community starts calling the last layer with all edges oriented "ZBLL".
The above screenshot is from the SpeedSolvingRubiksCube Yahoo group. It is the first mention of the acronym ZBLL. However, there may have been earlier mentions during the 1.5 years of messages that were deleted from the group.
Zbigniew Zborowski starts using the acronym everywhere, despite having previously acknowledged that Helmstetter and Petrus are who put in the work to create it.
Summary
Although the Petrus method already existed with an all edges oriented last layer, Bernard Helmstetter generated all of the algorithms to solve the Petrus method's last layer in a single step, and both Zborowski and Bruchem provided Helmstetter's algorithms on their own websites, the community named the step ZBLL. This is likely due to the popularity of CFOP at the time, the excitement at the time by CFOP users for ZBLS, and some being unaware of Helmstetter's algorithms. There was more interest at the time for ZBLS, so the CFOP community misnamed the last layer step ZBLL to go with ZBLS. If using people's names, the step should have been named after Helmstetter and Petrus. Petrus had the original method with all edges oriented on the last layer and was an influence for EO being integrated into CFOP. Helmstetter put in the work to generate all of the algorithms for the Petrus method to solve the all edges oriented last layer in a single step that were being used and promoted by both Zborowski and Bruchem.