Jack Armstrong, the All-American Boy was a radio series between 1933 and 1951. Every use of the term I remember as a child would have referred to that radio show, even though it ended before I started listening to radio.
My understanding was that the show was incredibly popular, and it would frequently get mentions & audio excerpts in, eg, Abbott and Costello movies that were filmed in that era (and which ran and reran on TV pretty much 24 hours a day up until maybe 1965).
The earliest reference that Ngram finds is 1938.
But apparently the term "All-American" with regard to sport goes back further. The Michigan Alumnus from 1922 contains:
The most recent Michigan player to be honored by an All-American berth
is Ernie Vick, '22, of Toledo, O., who was selected by Camp as center
because of his playing this past season.
And later:
In 1917 Camp did not select an All-American college team, but he did
pick an All-American Service team.
So apparently "All-American", in the sense of an outstanding sports figure, goes back to at least 1917.
And an issue of The Michigan Alumnus from 1902 appears to reference the same concept.
So I would link "All-American Boy" to the "Jack Armstrong" radio show, but the term "All-American" to earlier sports use.
From there I'll leave it to the sports fanatics to pin down the origin of "All-American".
Update
Well, since no one else is doing it, here is the apparent origin of "All-American" in the sports sense:
The College Football All-America
Team
is an honor given annually to the best American college football
players at their respective positions. The original usage of the term
All-America seems to have been to the 1889 College Football
All-America Team selected by Caspar Whitney and published in This
Week's Sports in association with football pioneer Walter Camp.
Camp took over the responsibility for picking the All-America team and
was recognized as the official selector in the early years of the 20th
century.
Note that the team is called the "All-America" team, presumably due to selecting the best players from across the country (*), but the members of the team were/are referred to as "All-Americans".
(*) Apparently even in 1899 there was dissension in the ranks as to whether the best players were being chosen, vs favoring those of the East Coast.
Looking at words beginning with ortho- there seem to be two possible pronunciations:
/ɔːrˈθɒ-/ as in orthogonal or orthography,
/ˈɔːrθə-/ as in orthodox or orthodontist,
where the second pronunciation has primary or secondary stress on the first syllable.
But in English phonology, the vowel /ɒ/ must be followed by a consonant, so the first pronunciation is ruled out for orthoepy. This is presumably what Walker meant when he said “Orthoëpy, having no consonant in the antepenultimate syllable, naturally throws its accent on the first” (1822).
You could also pronounce orthoepy /ɔːrˈθoʊ.iː.pi/. This seems to be what Robert Nares meant when he said that "the accented vowel is long in the antepenultima" (1782). However, there aren't any other words where ortho- is pronounced this way. I suspect this discouraged people from using it.
Best Answer
Etymonline to the rescue:
So the noun came first.