WestPak

IDA Pro's disassembler showing the resource which references the "WestPak.cpp" reference.

WestPak (more likely just referred to as PAK) was the name of a compression and file storage format which was created by Westwood Studios (likely used between 1991 and 1994) and which was used in the Ragnarok Online Alpha. Reverse engineering the Ragnarok Online Alpha binary reveals that the file "WestPak.cpp" is referenced in code, and the Alpha data.grf is compressed using this library, but subsequent versions use Gravity's own proprietary GRF format.