Whose calculations first suggested the Solar System was surrounded by a huge cloud of icy bodies?

Dutch astronomer Jan Oort suggested in 1950 that a vast spherical reservoir of icy objects surrounds the Solar System at extreme distances. This theoretical region is now called the Oort Cloud. It helps explain the origin of long-period comets, which can take thousands or millions of years to orbit the Sun. Although it has not been directly observed, it remains a central idea in planetary science.