Etymology: A combination of words, five & mouth to equal speak. *
Menmonic: FIVE MOUTHS SPEAK MANY WORDS
* This is a simplistic explanation as well (see previous post).
The character on right actually means the 1st person pronoun, I, and also match / resist. The idea was that a person uses words to match him or herself against another.
物語 (monogatari): saga
日本語 (nihongo): Japanese language