ALTERNATIVE FACTS: the origin of the phrase and its meaning.

Kellyanne Conway, an advisor to President Donald Trump, used the euphemism "alternative facts" when she was a guest on NBC’s Meet the Press on January 22, 2017, in a conversation with the show’s moderator Chuck Todd. 
"Press Secretary Sean Spicer Gave
Alternative Facts," says Kellyanne Conway.

Conway used this term to describe false statements made by press secretary Sean Spicer on January 21, 2017, the day after Donald Trump took office. Todd challenged her use of "alternative facts" immediately, saying, Alternative facts are not facts. They’re falsehoods." The term caught on widely with critics of the Trump administration.

In conversations about "alternative facts," the words post-fact and post-truth often come up. Post-fact and post-truth refer to an environment in which objective facts are a thing of the past. In a post-fact society, facts are viewed as irrelevant and emotional appeals are used to influence public opinion. This is not unlike Stephen Colbert’s concept of truthiness, which is trusting your gut feelings over facts. As his comical Colbert Report persona says, “Anyone can read the news to you. I promise to feel the news at you.”

The expression "alternative facts" evokes "Newspeak," the language of the fictional ruling party’s propaganda in George Orwell’s book, "1984." In the book, Newspeak leads to doublethink, which is when a person holds two contradictory beliefs in their mind at the same time and accepts them both. An example of doublethink from 1984 is the idea that “war is peace.”