Question

why is rajya sabha called the permanent body

Answer 1

Because in rajya sabha some members are also appointed by president .

they cannot be removed

Hence

Answer 2

Rajya Sabha or the upper house is a permanent body not subject to dissolution.
One third of the member retires every second year, and are replaced by newly elected members.
Each member is elected for a term of six years and so is a permanent house where members come and go out but the house is never empty.
Hope... it will help u.