What is Cha Tou one may ask? Literal translation is Tea Head. Does tea have heads and tails?! It means the odds and ends of something, tea in this case. For Dan Congs, Cha Tou are older leaves harvested in each season. Better ones are the Spring harvest of high elevation trees. Pu-erh cha tou are small batches of teas left after meeting the production quota. If 10,000 cakes of 400 g each are made, what's left are either call mao cha or cha tou depending on the condition and quantity that's left.
Chinese literature insinuates meanings deeper than its literal mean in daily use. Picture cutting up a whole fish or a chicken with head, skin, feet and gills, the best part of course is the main body and served as the main entree, however the head and tails are the "odds and ends", applying to tea production, the odds and ends are less sought after are called cha tou - tea head/tea tail, usually in small batches. Cha Tou-tea head is used most often as the tail is less appealing than the head (to some). :D