Scumph is the nasty yellow residue of something. For example the yellow stuff on the cigarette filter after it's been smoked. Or the yellow stuff that comes out of your ear when it hasn't been cleaned in a while. Anything dirty, sticky, yellow and that is a residue of something could basically be called scumph.

Internet persona(s) who happens to follow you and you happen to follow them back and maintain communication with and have a mutual liking for eachother whether it be friendship wise, etc. (Mutuals if more than one mutual)