There was the following paragraph in the article titled “How Russia wants to undermine the U.S. election” in Time magazine (October 10):
One day in June she (Arizona Secretary of state, Michele Reagan) was in her backyard in Phoenix when she got a call from her chief of staff. “Are you sitting down?” he asked. ---A group of hackers known as Fancy Bear was trying to sell a user name and password that belonged to someone in Arizona county election official’s office, which holds the personal data of almost 4 million people “My reaction was, well, this is like the worst thing that you want to hear,” Reagan recalls.
In other source – motherjones.com. (October 8), the phrase, “Are you sitting down?” is rephrased as “Can you sit down?'”:
Arizona Secretary of State Michele Reagan was in the backyard of her home last June when she got a call from her chief of staff. "The first words out of his mouth were, 'Can you sit down?'" Reagan told Mother Jones. He then said that her office had been "contacted by the FBI, and it looks like there's a computer password and username that belongs to our database for sale on the dark web." http://www.motherjones.com/politics/2016/10/state-election-hacks-undermine-voters-confidence
Are “Are you sitting down?” and “Can you sit down?” used to try somebody to brace for a shocking news, or calm down the other in advance?
What do they exactly mean? Are they very popular turn of phrases?