I'm not sure if I understand your first question, but I'll give it a whack...
It's from the Greek herpeton which means reptile (from herpein, to creep).
Het is short for heterozygous, which simply means an animal that has different alleles at one chromosol location. An organism requires the same alleles at a gene location in order to display that characteristic.
In snake terms, a heterozygous (or het) snake usually looks like a normal animal until it is bred with either another het or a homozygous snake, and if the offspring have the same alleles in that location then they will display that characteristic. An albino Het looks like a regular snake, but it has the potential to produce albino snakes.
