Question

why inert gases are called noble gases

Answer 1

they have stable electronic configuration so they have no need to react/combine with any other atom and remain inert(unreactive). Atom react to attain stable electronic configuration

if you write down the electronic configuration of noble gases the outermost shell remains completely filled

Answer 2

Inert gases are called noble gases because they were thought to be completely Inert - unable to form Compounds this is a reasonable belief because noble gases have complete octet making them stable nd unable to gain or lose any electron.