I’ve been watching the [Fullmetal Alchemist](https://en.wikipedia.org/wiki/Fullmetal_Alchemist:_Brotherhood) anime and noticed, that Edward’s arm prosthesis is called オートメイル, whereas in the subtitles it was written as 機械鎧. I couldn’t find this exact word with such reading in the dictionary. As far as I know, there is a [kind of words](https://en.wikipedia.org/wiki/Ateji), that utilize kanji but keep the borrowed reading, but with this word it doesn’t seem like the case, because there is no such word in the dictionary. I think I miss out on something. Did the creator of the story assign such reading? Is it common in Japanese to do such things?
by Zack_RL