cold-blooded (adj.) Look up cold-blooded at Dictionary.com
also cold blooded; 1590s, of persons, "without emotion, unfeeling;" of actions, from 1828. The phrase refers to the old notion that blood temperature rose with excitement. In the literal sense, of reptiles, etc., from c.1600. From cold (adj.) + blood (n.). Related: Cold-bloodedly; cold-bloodedness.