February 22nd is Ninja Cat Day in Japan. The onomatopoeia of a cat's meow in Japanese is nyan nyan. The Japanese love their homophones and thus nyan nyan become ni ni and the first syllable in the word ninja (忍者).
The kanji for nin is 忍 which means patience or self-restraint which are huge concepts in budo. The other kanji 者 is ja or sha which means person.
One of the major differences between beginners and experts is impulse control. Impulse control is nothing more than being able to control one's self in any situation. Self-restraint is then the mark of a true master.
Happy Ninja Cat Day!