Now, I in no way meant exactly a year, more in general usage, but seeing as you want to be pedantic about it, it's appeared in 20 threads in the past year, if you include misspellings by searching for *sinine As I remember, the word was used a couple of times a few years ago and ever since then it's been banded about frequently. I have not seen it used outside of these forums more than 2 or 3 times in the same number of years. If you introduce vocabulary to a closed community, it will become a part of their parlance, and that has been the case here.