Tattoo  Machines

Samuel O'Reilly invented the electric tattooing machine in 1891. O'Reilly improved upon an earlier tattoo machine invented by Thomas Edison that did not succeed commercially. Tattoo machines work by using a hollow needle filled with permanent ink. An electric motor pushes the needle in and out of the skin at a rate of up to 3,000 punctures per minute. The tattoo needle inserts a small of inkabout 1/8 of an inch below the surface of the skin each time.

Tattoo History : A Source Book
Online extracts from the book. A Brief History of Tattoos
The word tattoo comes from the Tahitian "tatu" which means to mark something."