Trying to get back on subject here... I was
reading something on sex laws, and came across an "urban legend" on the origin
of a certain four-letter word most of us love so dearly. Nothing I haven't
heard of before. It claimed it was an acronym of "for unlawful carnal
knowledge".
A more scientific etymology: West Germanic,
from the Dutch and German words for "to strike". It listed a possible IE
root: *peig- or *peik-.