The decigrade temperature scale is intended to simplify thinking about temperature in everyday human contexts, by stating temperatures in terms of numbers easily grasped by the human mind. Decigrade sets the freezing point of water to 0 degrees and the normal temperature of the human body to 10 degrees. This makes it possible to feel the difference between 0 and 10 degrees by means of holding an ice cube in one's hand.
Since the normal temperature of the human body varies, it cannot be used as part of a formal definition of the temperature scale, and consequently the decigrade scale is formally defined in terms of the boiling point of water which is 27 degrees.
The decigrade temperature scale originated with Vladimir Kornea, a Yugoslavian-born American who observed that he tended to think in terms of Celsius during winter and in terms of Fahrenheit during summer. He hypothesised that the reason for this is that the freezing point of water (0 Celsius) and the normal temperature of the human body (just under 100 Fahrenheit) made the ideal reference points of cold and hot in the context of weather.