Mrh Cows
Mrh Cow (or Mrh-Gaaz in zombese) is a derogatory term used to describe a survivor that upon zombification immediately proceeds to a designated revive point. Though the actual reason they are referred to as such is unknown, there is some speculation.
It is more than likely that the first part of the term derives from the Mrh Cow's vocabulary which consists entirely of the zombie word, "Mrh?". "Mrh" is one of the few zombie phrases available to zombies without Death Rattle. It is commonly used to request revives. A Mrh Cow in action sounds a bit like this:
"Mrh?" "Mrh?" "Mrh?" "Mrh?" "Mrh?" "Mrh?" "Mrh?" "Mrh?"
Additionally, the term Mrh Cow could be a play on the term "XP Cow". A gathering of Mrh Cows tend to be easy XP for both Zombies and Survivors, as the Mrh Cow will simply stand up and continue requesting revives when killed.
Another potential source for the term could be the phrase "Moo Cow", which young children often use to refer to Cattle. Also cow's moo's often have a mrh sound to them [1]
There are a few who call shooting zombies at a revive point "tipping" after rural pastime of cow tipping (gah zabbang). Some players have taken this practice up as a sport.
With "Combat revives" becoming rarer after the cost of syringe usage was raised from 1AP to 10AP, some players now consider Mrh-cowing to be a requirement of playing a survivor for any decent length of time, and for newbies to play one at all.