Simplify the following text for a Grade 9 native English-speaking person.
Original: The Vailala Madness acquired its name from observations of the behavior of people who participated in it , which included glossolalia , shaking and psychosomatic symptoms .
Simplified: The Vailala Madness got its name from the behavior of people who took part in it . This behavior included glossolalia ( or `` speaking in tongues '' ) , shaking , and signs of mental or emotional disturbances .