Japanese language purists carp about the surfeit of katakana, but as with all cultural manifestations, from bossa nova to breakfast cereals, the Japanese manage to make these linguistic borrowings their own in an unmistakable way, the most obvious being abbreviation.
Take tero, which means "terrorism." The English word has been around for a long time. Joseph Conrad defined its current usage in his 1907 novel, "The Secret Agent," which was about anarchists in London. The word has taken on heightened significance since 9/11, but regardless of how recklessly it is applied for political purposes the meaning is still the same.
In Japan, the word had very little local currency until the Tokyo subway sarin attack that occurred 10 years ago last weekend. The term used then was musabetsu tero, or "indiscriminate terrorism." Since then, musabetsu has been dropped and tero by itself has entered the language, without any need for modifiers. Considering how often the word is used to describe situations in the world now, not to mention incidents from the past that seem to fit (Japanese Red Army hijackings, North Korean kidnappings), tero is appropriate. Important words should be short, and "terrorism" can be difficult to pronounce, even for native speakers.