Original: Outside the cue sports industry, pocket billiards is (in English) more commonly referred to as pool, due to perhaps an association with the poolrooms where gamblers pooled their money to bet off-track on horse races.
Simplified: Outside the billiards industry, the various games played on these tables are very often called "pool". This is due to an association with the "poolrooms" where gamblers "pooled" together their money to bet on horse races.