Duggar, 24, and Seewald shared the big news on Monday through a video on TLC's website, saying the newborn was named after two "great" men: William Wilberforce and Matthew Henry.
Wilberforce was an inspiration and "real hero" to the pair because the British politician and author from the 1700s was "very instrumental in abolishing the slave trade and the British empire," according to Seewald.
"He was someone who really walked with God and his closeness with Christ and his joy that he had in the Lord really fueled his life and all that he did. That's why he was so relentless. Even after facing defeat so many times, he persevered and lived to see the day when the slave trade was made illegal throughout the British empire."
And as for their son's other namesake, Henry, Duggar apparently "really liked the name" and they "just thought it was cute."
"But also, there's another great man of God named Matthew Henry who lived before Wilberforce and he wrote a lot of great commentary. He actually has a whole commentary on the Bible," Seewald noted.
The pair's first son is named Spurgeon Elliot after the British preacher and author Charles Spurgeon. Duggar and Seewald seem to enjoy naming their children after brilliant writers.
"We were joking that people are going to start looking at the books on our fireplace mantle because we had a Spurgeon book up there before he was born, and we also have, on the right side of our fireplace, a six-volume set of the commentary of the Bible by Matthew Henry," Duggar revealed.