Originally I thought that chan is for the channel as on tv.
But in Japanese "chan" is term for cute as example cat/kitty-kitten
strangely the English language has no way even to translate that.
Guro is probably grotesque "Gurotesuku" as Japanese people can't spell anything without adding vowels everywhere
Ero guro nansensu, frequently shortened to ero guro or just guro, (エログロ ero-guro) is a literary and artistic movement originating c. 1930 in Japan. Ero guro puts its focus on eroticism, sexual corruption, and decadence. While ero guro is a specific movement, many of its components can be found throughout Japanese history and culture.
The term itself is an example of wasei-eigo, a Japanese combination of English words or abbreviated words: ero from "ero(tic)", guro from "gro(tesque)", and nansensu from "nonsense".
from Urban Dictionary:
"chan," usually used in the plural as "chans," can refer to the large array of English-language websites that were inspired by the japanese imageboard 2channel. The largest and most influential of the "chans" is the popular website 4chan , although there are many other similar websites such as 7chan, 420chan, wakachan, iichan, not4chan, gurochan, fchan, sidechan, renchan, and so on.