So I looked it up. And as close as I can tell there used to be a "watch" (a person who watches) in towns to wake people up and when clocks became miniaturized to something you could carry in a pocket (an amazing achievement in the 16th century), people called them the "watch" that wakes you up in lieu of the person. But that's sort of conjecture on my part based on the etymology that is there.
When I was studying Korean in the military I loved when they introduced Hanja, which is the Chinese characters used in the Korean language. For example, we memorized by rote how to say "hello" ("annyeonghaseyo") in Korean. But with the Hanja, we learned that the first syllable meant "peace" and the whole greeting meant (pretty much) "Be in peace." And that was so cool, I thought.
I have a theory about words. That is, the shorter they are, the more common they are. Think about short words: fork, plate spoon, knife, cup, food are all one syllable words. In less than 100 years the "horseless carriage" became the "automobile" and "auto" and "car" (despite governments' propensity to call them "motor vehicles"). I've already heard computers called "puters." Will that be shorten to "putes" or "comps"? "Telephone" became "phone." "Cellular telephones" became "cell phone" or just "cell" or "phone" or (as in the UK) "mobile."
If you're making up words when you write, you need to know about word origins. For example, you don't want to mix a Latin prefix with a Greek suffix. In my work in progress (the only one I have right now) I wanted to make up a word for someone who does magic with rocks and stones. Using "necromancer" as a basis for my word, I looked it up and learned it was a Greek word (that passed through Latin on its way to English). So I didn't want to say "lapismancer" or "petramancer" because "lapis" and "petra" are Latin. Looking what is Greek for stone (and remembering that scene in Raiders of the Lost Ark) I came up with "lithomancer." Then I googled it and found out it was an actual word.
(Why didn't I used "stonemancer" or "rockmancer"? because combining English and Greek is worse than Latin and Greek and sounds amateurish to me.)
Word origins can be fun and educational. So next time you look up a word in the dictionary check out its origin. You might have some fun.