Sucking the semen out of the fontanel (the soft spot in the top of a newborn baby's head) after the fontanel has been used for sexual gratification.
"Mr. Wooster, please take greater care when fontanelching. You have dribbled cum, blood and brains all over your dinner jacket." sighed Jeeves.
"Well, having sex with a baby's heads and drinking the semen from it is pretty standard operating p. at the Drones Club, Jeeves." Bertie exclaimed with relish, "And one can hardly fontanelch tidily".
From "The Sex Offender's Register of the Woosters"