How did Libra get its name?
Libra - Latin for "the Balance" or "the Scales", from the equivalent Greek word Zygos. This sign was originally called, "the Claws", which were attached to the constellation Scorpio; the later idea of a balance most likely derived from the relative equality of day and night at the autumnal equinox.
According to Michael Macrone (By Jove) at first Scorpio held the scales in his claw, but then the scales were transferred to Virgo, who used them to weigh various competing claims and thus to dispense her justice.
It looks as if in ancient times, poor Libra just kept getting jockeyed back and forth... back and forth... back and forth... and it seems as if the ancients had trouble making up their mind about Libra.