"I put the postcard in the envelope."
We use katakana for animal/plant's name. Apart from that, it is customary, i.e. cannot be explained.
Yes the examples you provided are of Japan origin, and the followings are examples commonly written in katakana.
- 葉書（はがき） postcard
- 鍵（かぎ） key
- 餓鬼（がき） brat
- 塵（ごみ） rubbish
- 皺（しわ） wrinkle
- 癖（くせ） perculiarity
- 駄目（だめ）no good
- 喧嘩（けんか） quarrel
An easy way to think these "something in something else" sentences is to just reverse the order of the english words. So if I put an envelope in the mailbox, the mailbox would take higher presedence and there for be first in the Japanese sentence. Think of the holder of the object as a higher priority.