On her husbands death she assumed the government, and fitted out an army for the invasion of Korea. She returned to Japan completely victorious after three years absence. Subsequently her son Ojin, afterwards 15th emperor, was born, and later was canonized as Hachiman, god of war. The empress Jingo ruled over Japan till 270.
As regards the English oath, usually By Jingo, or By the living Jingo, the derivation is doubtful. The identification with the name of Gingulph or Gengulphus, a Burgundian saint who was martyred on the 11th of May 760, was a joke on the part of R. H. Barham, author of the Ingoldsby Legends. Some explain the word as a corruption of Jainko, the Basque name for God. It has also been derived from the Persian jang (war), St Jingo being the equivalent of the Latin god of war, Mars; and is even explained as a corruption of Jesus, Son of God, Je-n-go. In
The article is originally from 1911 Encyclopedia Britannica
As the above is from the 1911 Encyclopedia Britannica, the 'history' of Empress Jingo and her involvement in Korea has been today, largely denounced by most historians and scholars as a myth, as the kingdom of Wa was not even consolidated while the Korean states were (Koguryo, Shilla, and Paekchae in the old Romanization).
As it is legendary, the invasion of Jingo of the Korean peninsula is based on Japanese interpretation of the Kwanggeto Stele found in Manchuria which proclaimed Koguryo's dominion of Manchuria and the northern part of Korea. Closer examination has revealed that the Japanese interpretation was pure conjecture since the three critical letters are in effect, missing, and in context would correlate more with Koguryo's immediate southern neighbors, the Shilla and Paekchae - the latter having very close relations with Japan including exchanges of the two courts and was a primary conduit of continental culture to Japan including the building of Japan's oldest wooden structure and temple.
Most Historians today, including Japanese scholars, typically reject the legend of Jingo as truth and refer instead to the close Japanese relations with the Korean state of the Paekchae.