A grandfather clock is a particular kind of clock. It is big, but that is not what "grandfather" means there. There are also new grandfather clocks.Originally Posted by jiang
We don't usually use "grandfather" for big or old. It can be used to imply experience. however. One can say "John is sort of the grandfather of the group." That would mean he has been with the group for a long time and probably has much information to share.
We do sometimes use "baby" a substitute for small or little. Baby steps are small steps. Baby carrots are small carrots. There is not added affection in most cases. "Baby" would just mean smaller than a normal variety.