chiefdom (n.)

c. 1300, "head, leader, captain; the principal or most important part of anything;" from Old French chief "leader, ruler, head" of something, "capital city" (10c., Modern French chef), from Vulgar Latin *capum, from Latin caput "head," also "leader, chief person; summit; capital city" (from PIE root *kaput- "head").

The meaning "head of a clan" is attested from 1570s; it was later extended to headmen of Native American tribes (by 1713; William Penn, 1680s, called them kings). Commander-in-chief is attested from 1660s.

abstract suffix of state, from Old English dom "statute, judgment" (see doom (n.)). Originally an independent word, but already active as a suffix in Old English (as in freodom, wisdom). Cognate with German -tum (Old High German tuom). "Jurisdiction," hence "province, state, condition, quality."