Question

which is the special name given to the instrument used to measure body temperature

Answer 1

the Liquid in glass thermometer is a special name given to the instrument used to measure body temperature .
Hope this was helpful

Answer 2

$\textbf{Clinical Thermometer }$ is the special name given to the instrument used to measure body temperature.

These are now adays also known as $\textbf{digital thermometer }$ as they used digital screen to visualise you with measured temperature.