When a male has intercourse with a female, the female gets energy and basically sucks the life out of the male causing him to be tired and ready for bed.
Semenergy aka Some Energy but the source of energy is given through intercourse.
Female: I'm so tired babe, I need semenergy.
Male: Let's go!
(male and female have intercourse)
Male: I'm ready for bed now. Did I give you enough energy?
Female: Oh ya! Thank you for giving me some semenegy babe!