by., I was delighted to see this thread, since I have a question, but it's too silly for Q&A.

At the hospital yesterday, I was struck by the thought that the sign I have seen so many times is actually rather odd:
Registration and Admitting.
Why isn't it either: Registrating and Admitting, or
Registration and Admissions? And for that matter, why isn't registrating a word? Or is it, Tsuwm?