Green’s Dictionary of Slang

(gay) the sucking of a man’s testicles by his partner.

1997–2002		Alt. Eng. Dict. 🌐 tea bagging (adj.) type of fellatio. The act of sucking the testicles.
1999		Indep. Rev. 28 Jan. 11: My father had to think about the term ‘T-bagging’ – where one man shoves or dunks his scrotum in the face of another.
1999		Roger’s Profanisaurus in Viz 98 Oct. 27: teabagging v. To make a strong brew with Fussells milk (qv) and two lumps. A last resort sexual practice whereby the man lowers his pods into the lady’s mouth.
2015		J. Stahl OG Dad 183: I think I accidentally tea-bagged my twins. Seriously, we were about to take a bath together [...] I felt these tiny little heads, like two croquet balls, against my underscrote.