This issue is merely on the margin of the discussion.
縁 refers specifically to the edge or brim of an object (e.g., a cup), whereas 周縁部 is broader and can refer to the outer area of a region or concept.
Compound of 周 (around, circumference), 縁 (edge, rim), and 部 (part, section). The word is a straightforward kanji compound with no irregular historical derivation.