Antonyms for "was made known" include "kept secret," "concealed," "hidden," "obscured," "unrevealed," "hushed up," "suppressed," "covered up," and "guarded." These words indicate the opposite of making something known or public. Instead, they suggest that information has purposely been kept from being disclosed. Sometimes, keeping information hidden can serve as a protective measure, but it can also be deceptive or manipulative. When using antonyms for "was made known," it is important to consider the context and the motives behind keeping information hidden.