Antedating of "knucklehead" (1938)

[Sam Clements]

M-W says 1942.
HDAS has 1942.  (They DO have a 1939 cite that uses "knuckleheaded," but
it's ambiguous:  "And you're just a knuckle-headed farmer girl."  More
below).
OED has 1944

>From the Nevada State Journal of June 26, 1938:

     "...Wm. "Bill" Hopper, president of the First National Bank of Nevada,
has decided to drag the novice or greenpea out into the open where all may
take a look and to the tune of a beautiful trophy and fancy cash prize, but
"ye knucklehead" must pay an entry fee to show his skill in the arena, and
natural skill it must be...."

It certainly predates a simple military explanation.  Implies a novice
rather than a stupid person.  Might the HDAS cite for "knuckle-headed farmer
girl" imply a novice/greenhorn rather than a dumbbell?

What do you make of this?

SC