You're looking for the term quisling, which is an adjective to describe someone (or a government or group of people) being a toady, particularly with respect to someone they should be standing up to. The term comes from Vidkun Quisling, who ran the Norwegian government during WWII. When the Nazis invaded, he actually helped them take over the country, and as a reward got to run it for them for a while. Churchill responded by making the man's name a byword for treason.
A vile race of Quislings—to use a new word which will carry the scorn
of mankind down the centuries—is hired to fawn upon the conqueror, to
collaborate in his designs and to enforce his rule upon their fellow
countrymen while grovelling low themselves.
It seems most likely that Wormtounge was in fact modeled upon Quisling. In fact, you'd have to invest some work to convince me otherwise. The Lord of the Rings was written from 1937-1941 just as all this was happening, and we know Tolkien was using the term himself in 1939 (before even Churchill).