This idiom derives from a German proverb, das Kind mit dem Bade ausschütten. The earliest record of this phrase is in 1512, in Narrenbeschwörung (Appeal to Fools) by Thomas Murner; and this book includes a woodcut illustration showing a woman tossing a baby out with waste water. It is a common catchphrase in German, with examples of its use in work by Martin Luther, Johannes Kepler, Johann Wolfgang von Goethe, Otto von Bismarck, Thomas Mann, and Günter Grass.
where does the saying don't throw the baby out with the bath water come from
a German proverb