x1 is Virgo [constellation/astrological sign].
From ferti. The Greeks and Romans associated Virgo with their goddess of wheat, Demeter-Ceres who is the mother of Proserpina-Persephone. For this reason the constellation became associated with fertility (in both Babylonia, Greece and Rome). Alternatively, she was sometimes identified as the virgin goddess Iustitia or Astraea, holding the scales of justice in her hand as the constellation Libra. Since ferti in lojban covers both potential and actual/realized fertility, the original meaning of the constellation have been chosen, but you could probably still interpret the name in both senses (as a deity of fecundity or as a fertile virgin).