Every year-end in Japan, we have a buzzwords contest where new and topical words are nominated. Lastly, the No.1 buzzword-of the-year will be chosen. These new words and phrases are often created by young generations, such as high-school-girls (so-called JK) and show-biz entertainers (e.g. comedians and politicians).
On the other hand, some words become unfashionable and gradually get phased out - this happens in all languages, not just Japanese. We call obsolete words “shi-go” (死語). “Shi(死)” means “dead”, so the direct translation is “dead words”. If you use “shigo” in a conversation, you might be mocked and embarrassed, so please don’t use “shi-go”!
A very interesting fact is that some of the words that are awarded as buzzwords often become obsolete words (“shi-go”) in the following years!!