'Settle' is Old English for 'to seat' — from PIE *sed- (to sit). Every meaning traces back to sitting down.
To resolve or reach an agreement about; to establish residence in; to sit or come to rest; to sink downward; (noun) a wooden bench with a high back and arms.
From Old English 'setlan' (to place in a seat, to come to rest, to establish), from 'setl' (a seat, a bench, a place for sitting), from Proto-Germanic *setlaz (a seat), from PIE *sed-tlo- (a thing for sitting on), an instrumental formation from *sed- (to sit). The noun 'settle' — a high-backed wooden bench — preserves the original concrete meaning and still survives in dialect. The verb extended step by step from 'placing someone in a seat' to 'establishing in a residence' to 'colonising' a territory
The PIE suffix *-tlo- (a place or instrument for performing an action) that formed *sed-tlo- (a place for sitting > settle) is the same suffix that appears in Latin 'pōculum' (a vessel for drinking, from 'pōtāre,' to drink) and in English 'throttle' (originally an instrument for the throat). The 'settle' (bench) is literally a 'sit-thing' — one of the oldest compound formations in the Germanic languages.