From SA-MP Wiki
PAWN (formerly known as Small) is the language that is used by SA:MP for game mode scripts, filter scripts and includes and was created by Dutch Company CompuPhase.
PAWN was created in year 1998, and was later ported in to SA-MP in 2006.
PAWN is a simple, typeless, 32-bit extension language with a C-like syntax. A pawn "source" program is compiled to a binary file for optimal execution speed. The pawn compiler outputs P-code (or bytecode) that subsequently runs on an abstract machine. Execution speed, stability, simplicity and a small footprint were essential design criteria for both the language and the abstract machine.
SA-MP is not the only project that is using PAWN, there are plenty of others.