Mousse a French term meaning ‘foam’, is applied to dishes with a foamy texture, usually cold and often sweet but also savoury and sometimes hot. The term was in common use in France by the 18th century. Menon (1758) has recipes for frozen mousses. Some confections are naturally foamy; others may need beaten egg white or whipped cream, and possibly gelatin, to achieve the desired texture.
It will be seen that, although a cold soufflé cannot be distinguished from a mousse, the latter name is used for a wider range of dishes.