Water can exist at many different temperatures, but only three of those temperatures have specific names: freezing, boiling, and lukewarm. Further, while freezing and boiling are determined by the molecular structure of the water itself (becoming a solid at 0° Celsius and a vapour at 100° Celsius), lukewarm is uniquely determined by the body temperature of the human who is dipping his or her toe into the water—about 38° Celsius. The word lukewarm first appeared in English at the end of the fourteenth century; before that, dating back to the early thirteenth century, the word luke was used by itself to signify the same temperature. In origin, the word luke derives from the Old English word hleow, meaning warm or tepid, which dates back at least to the tenth century. Beyond that, the origin of hleow is unknown, apart from its being related to the word lee, meaning shelter: mountains, for example, always have a lee side, a side sheltered from the wind and therefore warmer. Unrelated to the luke in lukewarm is the Luke in Matthew, Mark, Luke, and John; that biblical name derives from the Greek loukas, meaning man from Lucania, Lucania being a coastal region of southern Italy.