1
general::
Concoct fraudulently, fabricate, as in They trumped up a charge of conspiracy, or She had trumped up another excuse for not doing the work. This expression, first recorded in 1695, uses trump in the sense of "devise fraudulently," a usage otherwise obsolete.
American Heritage Idioms
2
general::
Phrase(s): trump something up
1. to promote or boost something. • They think they have to trump something up to get people to see it. • They trumped up the movie so much that many people were disappointed when it finally came out. 2. to think something up; to contrive something. • Do you just sit around trumping charges up against innocent people? • They trumped up the charges in an effort to disgrace me.
McGrawhill's American Idioms And Phrasal Verbs