("закон" - за коном, за границей допустимого, устоявшегося; "исконно" - из кона, из основы, из устоя, "на кону" - на основе, на базе, нечто важное, оберегаемое.
CON -
From Latin con-, from cum (“with”).
Prefix
con-
(non-productive) used with certain words to add a notion similar to those conveyed by with, together, or joint
congenial, congregation, console, consonant, construct, converge, etc.
(non-productive) used with certain words to intensify their meaning
confirm
Usage notes
Con- becomes
col- before l: collaborate;
com- before b, m, and p: combat, commit, compel;
cor- before r: correlation;
It can also appear as co-: coexistence, cosine.