noun. One who loves law.

His Bishop [Bp. Wren], that great Thesmophilist.
A discourse of proper sacrifice,ย Sir Edward Dering (1644)

Who among you loves law? Or any laws in particular? ย … No one? How unexpected. I don’t even think most lawyers areย thesmophilists. They know law because it’s their job, but love it? Nah.

Feel free to prove me wrong, I’m basing my comments on guesses and nothing else.

Thesmophilist could be easily used as a pejorative term. You know how much I love name-calling. Teach this one to your kids. “Okay honey, when the hall monitor threatens to tell on you, you just call him a dirty poo-poo thesmophilist and run away.”