The implication is that she is as polite and patient as a battalion of soldiers. Also, to a Japanese the term sounds like the name of an Anime superhero, whose energy the old hag possesses.
The previous definition was obviously written by someone whose knowledge of Japanese is limited to the word sushi. It's entirely wrong. And it's not true all Japanese words begin with a wovel. How about sushi?
From "oba" - grandmother, and "-tarian" - sounding like the kind of name an anime would give to a Godzilla-like creature.
Some foul-looking obatarian shoved me off the train.