Watch What You Say Around the Kids

My 3 y.o. was hiding at a corner of the living room playing by himself. Out of a sudden I heard him shout 'internal bleeding' twice. 

I was stunned for a moment. 

What did he just say? Did he say 'internal bleeding'? Huh? Who? What? 

I looked in his direction. He is fine. Still playing. Alone. 

I asked 'What did you just say, Chip?' 

Without looking up, 'Huh? Mummy, what did you ask?' 

I repeated. 

'Oh. Internal bleeding. I said internal bleeding. Cowy here (he held up his toy cow which he named 'Cowy') has internal bleeding because he hurt himself.' 

Ahh... kids are so cute! :) 

But E and I just have no idea where he has learnt that term from. Kind of worrying really.