From a (as a negative particle) and a presumed derivative of echo (in the sense of its congener schema); properly, shapeless, i.e. (figuratively) inelegant -- uncomely.
KJV: And those members of the body, which we think to be less honourable, upon these we bestow more abundant honour; and our uncomelyparts have more abundant comeliness.
NASB: and those members of the body which we deem less honorable, on these we bestow more abundant honor, and our less presentable members become much more presentable,