E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Lemnian Deed (A).
One of unusual barbarity and cruelty. The phrase arose from two horrible massacres perpetrated by the Lemnians: the first was the murder of all the men and male children
on the island by the women; and the other was the murder by the men of all the children born in the island of Athenian parents.