Ethymology of jukugo (compound character words)
Can anyone recommend a website or book about the ethymology of jukugo, compound character words?

So I want to be able to know HOW a combination of Japanese characters became to mean that specific word. For example 手紙. It means toilet paper in Chinese, but letter in Japanese. It is interesting for me to know the origin of this. Also it is easy for me to understand and remember the meaning of it. I want to be able to write kanji, not only read them.

So I am curious to the true ethymology of words like: 真面目、言葉、一生懸命

Question

Ethymology of jukugo (compound character words)
Can anyone recommend a website or book about the ethymology of jukugo, compound character words?

So I want to be able to know HOW a combination of Japanese characters became to mean that specific word. For example 手紙. It means toilet paper in Chinese, but letter in Japanese. It is interesting for me to know the origin of this. Also it is easy for me to understand and remember the meaning of it. I want to be able to write kanji, not only read them.

So I am curious to the true ethymology of words like: 真面目、言葉、一生懸命

Answer

Sorry to be pedantic, but the word is etymology, without the "h". In Japanese it's 語源 or 日本語の語源.

Any good website or book will be only in Japanese. If you're okay with that, you can try:

http://gogen-allguide.com
http://www.nihonjiten.com/gogen/nihongo/index.html

Search Amazon JP for 日本語の語源 and you'll find a decent selection.

There are also a couple of iOS apps (and probably some Android ones) although I haven't used them.

I often use "Do you know the origins of ___?" when I'm with Japanese people. Great conversation always ensues and most Japanese will be scrambling to check their phones and Wikipedia to see if you're pulling their leg or not with your answer, and telling you you know more about Japan than Japanese people do.