
1) Alonzo of the gridiron 2) Amos Alonzo of football 3) Early coaching great 4) Famed Chicago coach 5) Famed football coach 6) He invented the huddle 7) Immortal college coach 8) Legendary college coach 9) Legendary football coach 10) Name in football lore 11) Old man of football 12) Tackling-dummy inventor
Found on
https://www.crosswordclues.com/clue/stagg

1) Amos
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https://www.crosswordclues.com/clue/stagg
[tree] The Stagg tree (formerly known as the Day Tree) is a giant sequoia in Alder Creek Grove in California`s Sierra Nevada mountains. It is the fifth largest tree in the world and is believed to be over 3,000 years old. The tree was renamed around 1960 for Amos Alonzo Stagg (1862-1965), a pioneering football coach at the University of Chi...
Found on
http://en.wikipedia.org/wiki/Stagg_(tree)

D. J. Stagg (ed.), A Calendar of New Forest Documents 1244-1334, Hampshire Record Series 3 (1979), pp. 243-45.
Found on
http://info.sjc.ox.ac.uk/forests/glossary.htm

1862–1965, U.S. football coach.
Found on
https://www.infoplease.com/dictionary/stagg
No exact match found.