A misunderstanding of the old scientist/techie
joke that a millihelen is the amount of
beauty needed to launch one ship. Milli- is the international scientific prefix for
1/1000. Most international units are named after someone -- watt for power, newton for force, ampere for current, and so on. Scientists, techs, and gears who
work with those prefixes all the time often attach them to all sorts of made-up units. So a megahelen would be the
beauty of a
face that launched a billion ships (one million times one thousand) and a nanohelen would be the
face that launched one millionth of a ship (one billionth times one thousand). Millihelen worked better a few decades ago when newspapers and TV news often carried stories about ship launchings, because usually the
woman christening the ship launch was a First Lady, the Queen, or some senator or lord's wife (what nowadays we call a first wife, the one before the trophy wife), and thus a lizardy old bag that was only sort of recognizably female.
"That one's a mini-Helen."
"Unless she's a real cute
midget, you
mean she's got about a millihelen. Go back to chemistry class and stop getting your
science from Star Trek reruns!"