Etymology of 為替


為替 is a money order or exchange rate. How did they pick these two kanji? From
what I can tell, it's not kunyomi, onyomi, ateji, or gikun.




To add to ssb's explanation, what is usually called ateji are actually two
phenomena: 当て字 (音): to use kanji only for their sound, eg 矢鱈 義訓 (訓): to use
kanji for their meaning, and assign a fitting word to the kanji (compound), eg
為替

It's often not necessary to distinguish between these two methods (of writing
words), but it's something to keep in mind.

Also, 為替 is the 連用形 of 交わす.

