Since we heard last chapter that her name is slang for testicles, it must be funny to hear this from her POV. To her he is just saying testicles over and over.
@KeiosKod I guessed he just dropped the suffix, so an English comparison would be going from calling her "Mrs. Testicles" to "My dear Testicles" or somesuch. (And her real name is like Hestia.)