I was born in the 1970's and it is lost on me too, I think its something that became a thing to the generation after me

I think it comes from an episode of Sabrina the Teenage Witch and exploded as a meme.

I think it's just the most simplified you can get talking about cellular biology, specifically when teaching organelles. So most primary science textbooks use that terminology and it's more memorable than all the other organelles so it just stuck and it got repeated and reviewed every year and it sorta became a pre Internet meme and part of a shared consciousness if you were schooled in the US.

6th grade biology class in the United States, 2001 AD.

The teacher slaps up a diagram of a cell and organelles.

30-45 children all looking around the room, not exactly paying attention

She points to the various organelles, trying to explain their purpose, the golgi complex, ribosomes..

"And the mitochondria"

"Is the power house of the cell"

Children cheer in applause and repeat it, because it rhymes.

It then enters the collective unconscious of English speakers.

I was in the room where it happened.

We actually had the same sentence as the headline for the chapter about mitochondria in our class in the late 90s, just translated. "Mitochondrien - das Kraftwerk der Zelle"