The cliffs take their name from an old promontory fort called Mothar or Moher, which once stood on Hag's Head, the southernmost point of the cliffed coast, now the site of Moher Tower. The writer Thomas Johnson Westropp referred to it in 1905 as Moher Uí Ruis or Moher Uí Ruidhin. The fort still stood in 1780 and is mentioned in an account from John Lloyd's A Short Tour of Clare (1780). It was demolished in 1808 to provide material for a lookout/telegraph tower that was intended to provide warning in case of a French invasion during the Napoleonic wars.