1 occupy (as a settler) or be occupied (by settlers).
1859  By that means the trader would have followed the miner, and settled up the country, and thousands who have left our shores would have remained to add millions to our productive wealth.
1921  The country began to settle up very rapidly and business with the Hudson's Bay Company assumed . . . large proportions. . . .
2 pay a debt; honor a commitment.
1910  "All right, I'll settle up with you later on."
1964  Down to 45 years ago, a planter would often "ship" a girl as a house servant by a brief formal agreement written out and filed in his merchant's office, the servant thereafter drawing her small needs from the shop on credit, and her account being credited and the planter's account per contra debited, at settling up time with her agreed very small wage.