E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
The earth. When Junius Brutus and the sons of Tarquin asked the Delphic Oracle who was to succeed Superbus on the throne of Rome, they received for answer, He who shall first kiss his mother. While the two princes hastened home to fulfil what they thought was meant, Brutus fell to the earth, and exclaimed, Thus kiss I thee, O earth, the great mother of us all.