It's not specific to trading.
https://en.oxforddictionaries.com/definition/shillshill
NOUN
North American
informal
1 An accomplice of a confidence trickster or swindler who poses as a genuine customer to entice or encourage others.
‘I used to be a shill in a Reno gambling club’
figurative ‘the agency is a shill for the nuclear power industry’
More example sentences
1.1 A person who pretends to give an impartial endorsement of something in which they themselves have an interest.
‘a megamillionaire who makes more money as a shill for corporate products than he does for playing basketball’
VERB
[NO OBJECT]
North American
informal
Act or work as a shill.
‘your husband in the crowd could shill for you’
You probably hear people being accused of shilling for particular coins or projects. Name calling is pretty common in this space.