I'm finding dozens of the phrases I would naturally use, I can't use on my new planet. "... face changed from bulldog to guilty puppy": They don't have dogs on the planet. If I say looking like a guilty [insert other named animal] will the readers relate? I'm reading Dan Simmons' "Endymion", the third book in the Hyperion series. He has an entire invented vocabulary of technical things: fat lines, Hawking Matt, fleshette guns, and so on. Anyway, I need to develop a whole new vocabulary including some new idioms. I'm considering creating a dictionary for my world building. Do we still use colloquialisms or idioms with past things no longer in existence in the present? I'm wondering if I can get away with old Earth colloquialisms 4-5 generations later on a new planet?