Wasei-eigo (和製英語) means “Japanese-made English”. These words are derived from existing English words or combinations of them, that have a different meaning than the original word or simply do not exist in standard English.
Wasei-eigo is often confused with gairaigo (外来語), which are loan words with the same meaning as the original word. Unlike wasei-eigo, garaigo also uses words of other origin than English.
The word misappropriation in wasei-eigo often comes from misunderstandings and improper word use. One famous example is the word バイキング (baikingu / viking). This word doesn’t indicate the viking as in old Norse seafarers, but an “all-you-can-eat buffet”. The origin is from the first all-you-can-eat restaurant in Japan called “バイキング”. One of the things that popularized it was a scene from the 1958 movie “Vikings” where the vikings were eating a lavish meal.
Other examples are “カンニング” (kanningu / cunning), which means “cheating on an exam”; “クレーム” (kureemu / claim), which means “complaint”; “ベビーカー” (bebiikaa / baby car) which means “stroller”.
The use of wasei-eigo is most likely due to the media, which makes use of strange English term when advertising new products in order to give a better image to the product, as the use of English within Japanese phrases can make a good and lasting impression in Japan.