Making something unclear, obscure, or less transparent, either physically or mentally.
From Old English 'clūd' meaning a lump of earth or cloud. The metaphorical use of 'clouding judgment' developed in Middle English as people compared unclear thinking to actual clouds obscuring the sky.
Our brains are literally using a visual metaphor when we say emotions 'cloud judgment'—we're describing confused thinking using the same word as actual weather! Ancient people made this exact comparison.
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