What does 'hit the fan' mean?

Read the following excerpt from the play a raisin in the sun by lorraine hansberry: johnson (this usa woman who decided long ago to be enthusiastic about everything in life and she is inclined to wave her wrist vigorously at the heigh of her exclamatory comments.): hello there, yourself! h’you this evening, ruth? which assumption about johnson is most likely true based on the stage direction? a. her enthusiasm is used to mask her fear of public places