A suffixal form ᴱN. -carn or -garn of the passive participle agarn for the verb ᴱN. cara- “to make, do” in the Early Noldorin Dictionary of the 1920s, hence meaning something like “-*made”.

Neo-Sindarin: I think this suffix can be salvaged as a reduction of the later passive participle carnen of S. car- “do, make”, which can be used to form adjectives such as adangarn “man-made”. It does conflict with S. carn “deed”, but I prefer S. carth for this noun form.