What common name is used to describe both the taste and the olfactory receptors and why?

The name is chemoreceptors; this is because they both respond to chemical in solution. A receptor is a protein molecule that receives chemical signals from outside a cell. When such chemical signals bind to a receptor, they cause some cellular/tissue response; e. g. a change in the electrical activity of a cell. Chemoreceptors are cells specialized to detect chemical substances and relay that information centrally in the nervous system. Chemoreceptors may monitor external stimuli, as in taste and olfaction, or internal stimuli, such as the concentrations of oxygen and carbon dioxide in the blood.