|Noah Webster's Dictionary|
(n.) The state or quality of being stout.
Int. Standard Bible Encyclopedia
stout, stout'-nes: In modern English the word signifies strength firmness, corpulence, etc., but in English Versions of the Bible (Psalm 76:5 Isaiah 10:12; Isaiah 46:12 Daniel 7:20 Malachi 3:13 with stoutness" in Isaiah 9:9) it always means "bold" or "proud" and invariably in a bad sense; compare the German stolz, with which "stout" is allied.
Stoutness (2 Occurrences)
Isaiah 9:9 And all the people shall know, even Ephraim and the inhabitant of Samaria, that say in the pride and stoutness of heart, (KJV ASV DBY WBS)
Isaiah 10:12 And it shall come to pass, when the Lord hath performed his whole work upon mount Zion and upon Jerusalem, I will punish the fruit of the stoutness of heart of the king of Assyria, and the glory of his high looks. (DBY)