The original Rintintin was one of a pair of Parisian street urchins ('titis' in Parisian slang) drawn as a cartoon by a French Artist in 1913 and called Nénette et Rintintin. The little cartoon couple became famous throughout France during WW1 because of a popular song and people made little dolls representing the couple out of bits of left-over wool. Paris was not occupied during WW1 but it was during WW2 when the artist who drew Nénette et Rintintin was put under house arrest for designing patriotic posters, cartoons and cards during WW1.
The drawings and song depicted the couple as escaping unscathed from the various bombardments that Paris was subjected to during the First World War, so they were made into good luck charms and also brooches and distributed widely. The artist designed a postcard with the woollen dolls pictured on it with a little poem and these were sent to troops at the Front for luck, which may be how Lee Duncan knew about them.
Once they were weaned, Duncan chose two puppies for himself - a male and female - and called them Nanette and Rin Tin Tin. He took them back to America with him after the War - Nanette died but Rin Tin Tin survived. Lee Duncan trained his dog and the rest, as they say, is history. Rin Tin Tin lived until 1932, starred in 27 films and even had his own radio show from 1930 - 1932. Duncan took the body of his dog back to Paris where Rin Tin Tin is buried. There were eleven more dogs, reportedly related to the original Rin Tin Tin, after his death and a TV film series was also made using his name.
Note: “titis” is a word in Parisian slang meaning ‘street children’. For fans of “Les Miserables”, Gavroche is a ‘titi’. "Titi"is also the name used in France for Tweetie Pie the cartoon character.