Mormo

Mormo (, "Mormō") or Mormon was a female spirit in Greek folklore, whose name was invoked by mothers and nurses to frighten children to keep them from misbehaving.
The term mormolyce (; pl. "mormolykeia" ), also spelt mormolyceum ( "mormolukeîon"), is considered equivalent.
Etymology.
The name "mormo" has the plural form "mormones" which means "fearful ones" or "hideous one(s)", and is related to an array of words that signify "fright". 
The variant "mormolyce" translates to "terrible wolves", with the stem "-lykeios" meaning "of a wolf".
Description.
The original Mormo was a woman of Corinth, who ate her children then flew out; according to an account only attested in a single source. Mormolyca (as the name appears in Doric Greek: ) is designated as the wetnurse () of Acheron by Sophron ( 430 BC).
Mormo or Moromolyce has been described as a female specter, phantom, or ghost by modern commentators. A mormolyce is one of several names given to the female "phasma" (phantom) in Philostratus's "Life of Apollonius of Tyana".
Mormo is glossed as equivalent to Lamia and "mormolykeion", considered to be frightening beings, in the "Suda", a lexicon of the Byzantine Periods. Mombro () or Mormo are a bugbear (), the "Suda" also says.
"Mormo" and "Gello" were also aliases for Lamia according to one scholiast, who also claimed she was queen of the Laestrygonians, the race of man-eating giants.
Bugbear.
The name of "Mormo" or the synonymous "Mormolyceion" was used by the Greeks as a bugbear or bogey word to frighten children.
Some of its instances are found in Aristophanes. Mormo as an object of fear for infants was even recorded in the "Alexiad" written by a Byzantine princess around the First Crusade.
Modern interpretations.
A mormo or a lamia may also be associated with the empusa, a phantom sent by the goddess Hekate.