Is the word settled a common noun?

No, the Word settled is a verb, the past participle, past tense of the verb 'to settle'; a Word for the act of establishing a permanent place to live; the process for solid particles in a liquid to sink to the bottom or an object or to sink into the ground; to conclusively resolve a conflict; a Word for an action.

The past participle of the verb is also an adjective, a Word that describes a noun.

The noun forms of the verb to settle are settler, settlement, and the gerund, settling.