[see COLD a. 7 b.] A phrase of the older physiology: from the sensations felt in the face and head when the circulation is quickened by exertion or excitement, the blood itself was supposed to grow hot or to ‘boil,’ at other times to be ‘cold’ or not sensibly hot. See BLOOD 5. Hence phrase in cold blood: a. Coolly, without excitement, not in a passion; with sang froid; b. Now chiefly in reference to doing with cool deliberation things which look like the cruel deeds of passion.
a. a. 1608. Sir F. Vere, Comm., in Arb., Garner, VII. 95. A resolution framed in cold blood.
a. 1642. Sir W. Monson, Naval Tracts, III. (1703), 330. Punishment is fittest to be executed in cold Blood, the next day.
1712. Addison, Spect., No. 407, ¶ 1. We can talk of Life and Death in cold Blood.
1875. Whyte-Melville, Riding Recoll., ii. (ed. 7), 21. To ride him over a fence or two away from other horses in cold blood.
1881. Mrs. P. O’Donoghue, Ladies on Horseback, I. iii. 42. A horse … greatly dislikes being brought to his fences in cold blood.
b. 1711. Addison, Spect., No. 44, ¶ 5. It … looks like killing in cold Blood.
1757. Smollett, Reprisal, II. xv. We Englishmen never cut throats in cold blood.
1879. Froude, Cæsar, viii. 73. A few thousand prisoners were taken, but they were murdered afterwards in cold blood.
