means Brought to a state of stability, resolution, or calm — whether describing a dispute that's been resolved, a person who's grown stable, or a place where people have put down roots.

from From Old English 'setlan,' to seat or place, built on 'setl' — a seat or dwelling-place (a cousin of the modern word 'settle,' the long wooden bench). The thread running through all its senses is the image of coming to rest: putting something down where it stays, the way a sediment sinks or a body lowers into a seat. From that literal sitting grew the figurative settling — of arguments, of nerves, of frontier land — all of them the act of making something finally stop moving.