E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
literally means what embraces or contains, and the idea implies that the colour of the skin corresponds to the habit of body, and the habit of body answers to the element which predominates. If fire predominates, the person is bilious or full of bile; if air, he is sanguine or full of blood, if earth, the body is melancholic or full of black bile, if water, it is phlegmatic or full of phlegm. The first is hot and dry, the second hot and moist, the third cold and dry, and the last moist and cold like water.
Tis ill, tho different your complexious are [i.e. dispositions].