They are called snake bites as a snakes fangs puncture two holes next to each other, ie. the two holes through the skin under the lip next to each other.
Snake bites used to mean two piercings next to each other anywhere on the body, but are now more recognised as the lip type as these seem to be the most popular.
"I'm getting two lip piercings, one on either side."
2 - "Really? I was thinking of getting some, but I didn't have the money."
A favourite of Irish and English Goths/metal heads/rockers and Austrialians.
If visiting America be careful! If you ask for a snakebite in an Irish bar you may find the taste of Gunniess making it way in to your mouth. Gunniess is used instead of larger by some, a vile practice.