Article about Entertaiment:
The capacity of entertainment to cross over media and to recur in familiar forms has given it the power to sustain the interest and captivate the imagination of many people throughout the ages. But there is a limit to how much entertainment can really entertain, and what seems entertaining to one person may be distasteful or even cruel to another.
From late 15c., when it became a suffix (like -ment) for nouns formed from verb stems that had been used as auxiliaries in Latin (beginning-e-ment, better-e-ment, merriment, etc.). It was influenced by French entre- and tenir, and by a Latin habit of inserting -mentum after e- in some nouns.
See also amusement, diversion, pleasure.