Settle (v.) "come to rest," Old English
setlan, from
setl "a seat". Sense of "establish a permanent residence" first recorded 1620s; that of "decide" is 1620s. Meaning "reconcile" (a quarrel, differences, etc.) perhaps is influenced by Middle English
sahtlen "to reconcile," from Old English
saht "reconciliation," from Old Norse
satt "reconciliation." Related: Settling. Settled "firmly fixed" is attested from 1550s.