Negation of the active participle
The negation verb 
tm is used to negate the active participle form. It is notable that the negative verb always takes the form of what it negates, while the original verb turns into a negatival complement.
mdt mAt tmt swA
New talk which has never (yet) passed.
The verb tm assumes form of an active participle indicating the past or perfective. As for the original verb swA, it is a negatival complement.