Altered Dad
When I was about 7, we had a male cat which my mom took to the vet to be "altered." When I asked what that meant, rather than go into great detail at the time, my mom just gave me the following "simple explanation."
"Altered means the cat will not leave home anymore," she said.
Good enough answer for a then seven year old! Keep it simple, right?
Later that week, we had a number of people over for dinner. My dad was often away on business and Mother had 5 children to handle on her own when he was traveling. Someone at the table commented about how difficult it must be to have my father away so much and for her to have to deal with 5 children, mostly alone much of the time.
Knowing just how to help, I blurted out, "Hey Mom, why don't we just have Dad altered so *he'll* stay home from now on?!"