Grass is really difficult to eat. Even if you can manage to chew it up (and you won't do it with human teeth) then getting any goodness out of the stuff is horribly difficult.
Rabbits and elephants do it by putting the grass through their systems twice, but unfortunately this does involve eating their own poo. A cow has four stomachs to digest its grass but actually needs five, so it has to bring up the grass from its first stomach and give it another good chewing.
This is called chewing the cud.
On the whole I'm glad humans don't eat grass. Humans do sometimes chew tobacco, though, and a piece of chewing tobacco is called a quid, which is basically the same word as cud.
Much less likely to turn your teeth orange, however, is chewing the cud in the sense of having a long relaxed chat, probably about how to solve all the problems of the world. This seldom takes more than an hour or so, or about three drinks.
Thing To Do Today: chew the cud. Cud is from the Old English word cwidu, which means what has been chewed. It's related to the Old Norse kvātha, resin (resin was the original chewing gum) and the Old High German quiti, which means glue, and the Sanskrit jato, which means rubber.