The phrase "
like water for chocolate" comes from the Spanish "como agua para
chocolate." This phrase is a common expression in
Spanish speaking countries and was the inspiration for
Laura Esquivel's novel title (the name has a double-meaning).
In Latin American countries, such as Mexico, hot chocolate is made not with milk, but with water instead. Water is boiled and chunks of milk chocolate are dropped in to melt. When someone is "like water for chocolate," it's comparable to saying "they're at the boiling point," because that's the point water has to be at to make the hot chocolate.