Meme
"Meme" is a word coined by evolutionary biologist and zoologist Richard Dawkins (in his book The Selfish Gene) as the unit of cultural inheritance, analogous to a gene (the unit of biological inheritance). The word is pronounced to sound like "gene". In the book, Dawkins argued that ideas behaved analogously to selfish biological replicators, being passed down from generation to generation and occasionally experiancing a change (mutation) which made them more popular.
The term is important to the YTMND community because of the meme-like fashion in which its fads come and go. Furthermore, the spread of YTMND sites across the internet can also be said to follow a meme-like pattern.
The theory of memetics is controversial, and not everyone accepts that the analogy is entirely fitting.