Well, we just got back from a trip to Texas, and I'm still in get-situated-back-at-home mode, so this will be a short one. =) But last week I had to look up when grandfather clocks came to be called grandfather clocks (can't believe I even thought to question that one), and was surprised by the answer, so . . . ;-)
Grandfather itself is from the 15th century, a compound word of pretty obvious origins. It replaced "grandsire" and the Old English ealdefaeder.
There aren't many phrases that use it--there's "grandfather clause," which referred to exemptions from post-Reconstruction voting and restrictions in the South for men whose family members had voted before the Civil War. That came about near the turn of the century.
And then, ta da, grandfather clock. This is from the 1880s and apparently refers to a song--don't ask me which one, LOL. Before that--which is to say, for in my story, which is a far sight earlier--they were just called "tall case clocks" or "eight day clocks."
So there you have it. A few little tick-tocks to learn about the grandfather clock. =) Now I need to go unpack some bags . . .