It started with the French.

https://en.m.wikipedia.org/wiki/History_of_the_metric_system

The meter was originally based on the measured dimensions of the Earth.

I think there were multiple competing suggestions at the time, the grandfather clock was one while the standard ended up being the French proposed one that you mention

Ah yes, you're right. Another nice coincidence that a seconds pendulum is less than 1% away from 1/10 millionth the distance between the equator and poles.