echolalia

"Echolalia is a mental disease which makes people immediately repeat things that well people around them say. But Billy didn't really have it. Rumfoord simply insisted, for his own comfort, that Billy had it. Rumfoord was thinking in a military manner: that an inconvenient person, one whose death he wished for very much, for practical reasons, was suffering from a repulsive disease."

-Kurt Vonnegut, "Slaughterhouse-Five".