Yellow Journalism had originated after there was a growth in the usage of newspapers. Newspapers had rapidly gotten more popular due to the low prices, and also because it was the primary source of news for everyone.
Since newspapers had gotten so popular, it was becoming important for each newspaper company to present news, each in a unique way and each in a race with each other to present the news first. Competition had gotten so bad that newspaper companies were going as far to making up information and exaggerating on details in order to catch the viewers attention.
Now for the term “Yellow Journalism”, this had come to be based upon a comic character that was called the “Yellow Kid” because he had a lot going on his comic panel, just like how the news had a lot going on when it was being exaggerated.