may mean the subterraneous, or the goddess of the earth, that is, the protectress of the fields, whence it is used as a surname of infernal divinities, such as Hecate, Nyx and Melinoe, but especially of Demeter.
Although the name, in the case of Demeter, scarcely requires explanation, yet mythology relates two stories to account for it.
According to one of them, Clymenus and Chthonia, the children of Phoroneus, founded at Hermione a sanctuary of Demeter, and called her Chthonia from the name of one of the founders.
According to an Argive legend, Demeter on her wanderings came to Argolis, where she was ill-received by Colontas. Chthonia, his daughter, was dissatisfied with her father's conduct, and, when Colontas and his house were burnt by the goddess, Chthonia was carried oif by her to Hermione, where she built a sanctuary to Demeter Chthonia, and instituted the festival of the Chthonia in her honour.
CHTHONIUS has the same meaning as Chthonia, and is therefore applied to the gods of the lower world, or the shades and to beings that are considered as earth-born. It is also used in the sense of "gods of the land," or "native divinities."
There are also several mythical personages of the name of Chthonius.