
1) Affections 2) Grit 3) Guts 4) Heart 5) Nerve 6) Spunk 7) Strength 8) Valor 
Found on 
https://www.crosswordclues.com/clue/mettle

1) Bravery 2) Courage 3) Courage and fortitude 4) Courage, spirit 5) Courage; spirit 6) Courageousness 7) Exclusively Anglo word 8) Exclusively Saxon word 9) Fighting spirit 10) Fortitude 11) Grit 12) Gumption 13) Heart 14) Inner fiber 15) Inner strength 16) It may be tested 17) Marvel Comic superhero 
Found on 
https://www.crosswordclues.com/clue/mettle

• (n.) Substance or quality of temperament; spirit, esp. as regards honor, courage, fortitude, ardor, etc.; disposition; -- usually in a good sense.
Found on 
http://thinkexist.com/dictionary/meaning/mettle/

Substance or quality of temperament; spirit, especially. As regards honor, courage, fortitude, ardor, etc.; disposition; usually in a good sense. 'A certain critical hour which shall.. Try what mettle his heart is made of.' (South) 'Gentlemen of brave mettle.' (Shak) 'The winged courser, like a generous horse, Shows most true mettle when you check ...
Found on 
http://www.encyclo.co.uk/local/20973
 Met'tle  noun
Met'tle  noun [ English 
 metal , used in a tropical sense in allusion to the temper of the metal of a sword blade. See 
 Metal .] Substance or quality of temperament; spirit, esp. as regards honor, courage, fortitude, ardor, etc.; disposition; -- usually in a good sense. « A certain criti...
Found on 
http://www.encyclo.co.uk/webster/M/60

 quality of endurance or courage 
Found on 
http://www.graduateshotline.com/list.html

Mettle is British slang for semen.
Found on 
http://www.probertencyclopaedia.com/browse/ZM.HTM
 [Macbeth]
[Macbeth] (74) courage
Found on 
https://www.cliffsnotes.com/literature/m/macbeth/study-help/full-glossary
 spunk noun
spunk noun the courage to carry on; `he kept fighting on pure spunk`; `you haven`t got the heart for baseball`
Found on 
https://www.encyclo.co.uk/local/20974
 [SAT terms]
[SAT terms] the courage to carry on
Found on 
https://www.vocabulary.com/lists/151399

 the courage to carry on
Found on 
https://www.vocabulary.com/lists/388513
 [Intelligent words]
[Intelligent words] the courage to carry on
Found on 
https://www.vocabulary.com/lists/52473
 [Wise words]
[Wise words] the courage to carry on
Found on 
https://www.vocabulary.com/lists/907466
  No exact match found.