It originated from an episode of "Even Stevens" when Louis' crazy uncle comes to town causing trouble.
The scene where the phrase "foo clad" takes place when Louis got into an argument with his dad because he was supposed to be washing the car but instead hung out with his crazy uncle.
Louis: Well too bad.
Steve: What did you say?
Louis: I said...foo...clad.
Steve: FOO CLAD!?
While our lifespan is the number of years we will live, our healthspan is the number of healthy years we will have and our sexspan is is the number of years we will continue to be healthy enough to continue having an active sex life.
A lighthearted reaction upon receiving disappointing news of some sort. Usually something that isn't a particularly a big deal, esp. when it primarily affects someone else - sort of a mild schadenfreude. Sometimes doubled or tripled, and possibly said in a sing-songy voice for added comedic effect to imitate a muted trumpet, which is how the meme originated.