If Churchill said it, he was repeating George Santayana. I imagine the original phrase was in Spanish, because I see about 12 different versions on the net.
It seems to be rendered roughly as
"Those who do not remember their history are doomed to repeat it."
This phrase has often been used, tongue in cheek, by history teachers on the importance of studying.
\"What are you talking about? One, two, three, fo-- oh, crap.\"
- G. Edwin Bergstrom, Arlington VA, 15 Jan 1943