Is it speaking of his girth or his countenance?

Daniel 7:20 And of the ten horns that were in his head, and of the other which came up, and before whom three fell; even of that horn that had eyes, and a mouth that spake very great things, whose look was more stout than his fellows.

Because of?

Isaiah 10:12 Wherefore it shall come to pass, that when the Lord hath performed his whole work upon mount Zion and on Jerusalem, I will punish the fruit of the stout heart of the king of Assyria, and the glory of his high looks.

Or like?

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,