From the MySQL documentation:
"The next two sections discuss COLUMNS partitioning, which are variants on RANGE and LIST partitioning that were introduced in MySQL 5.5.0."
"The discussions of RANGE COLUMNS and LIST COLUMNS partitioning in the next two sections assume that you are already familiar with partitioning based on ranges and lists as supported in MySQL 5.1 and later; [...]"
My guess would be that partitioning was added in 5.1 and the COLUMNS option was added in 5.5.0.