“Living under a rock” (uninformed)

Someone who has been “living under a rock” is someone who doesn’t know even the most popular cultural events. A person “living under a rock” has no media—no radio, no television, no newspapers and no Internet. The expression “living under a rock” implies that the person came straight from the stone age.
 
“Liberty has been living under a rock” was cited in print in May 1945. American singer and actor Frank Sinatra (1915-1998) popularized the term in December 1954 in a United Press news story:
 
“‘I added that if he didn’t know who Judy Garland was, he must have been living under a rock,’ Sinatra said.”
   
 
11 May 1945, Zanesville (OH) Signal, “Id Rather Be Right” by Samuel Grafton, pg. 4, col. 6:
(German Foreign Minister—ed.) Von Krosigk’s speech is curiously complete, for he also trots out the idea of “liberty.” Liberty has been living under a rock in Germany for a dozen years, but Von Krosigk wipes the mold off it, and exhibits it, blinking stupidly in the sun.
 
Google News Archive
12 December 1954, Victoria (TX) Advocate, “Sinatra Tells Cause Of Recent Fight” (UP), pg. 18B, col. 5:
“I added that if he didn’t know who Judy Garland was, he must have been living under a rock,” Sinatra said.
   
Google News Archive
15 August 1973, Lodi (CA) News-Sentinel, “Reagan confident in Ed Reinecke” (UPI), pg. 3, col. 2:
“I am aware of what is going on,” Regan said. “You’d have to be living under a rock not to be.”
 
Google Books
Flashpoint
By George La Fountaine
New York, NY: Coward, McCann & Geoghegan
1976
Pg. 129:
“You live under a rock, pal?”
 
8 January 1980, Boston (MA) Globe, “Reagan hits Carter on grain curb” by Rachelle Patterson, pg. 1:
Asked about Connally’s remark during the debate that Reagan’s stand on the issues is not clear, Reagan said: “Connally must have been living under a rock.”
   
OCLC WorldCat record
MICHAEL CROWLEY: UNDER A ROCK Where Steve Forbes got his campaign staff
Publisher: New York : The Republic Pub. Co.,
Edition/Format: Article : English
Publication: The new republic. (January 29, 1996): 22
Database: ArticleFirst
 
Urban Dictionary
live under a rock
someone who is oblivious of the outside world
Have you seen this movie
No
How?! you live under a rock
by Tomas!  Dec 26, 2010
 
YouTube 
Do you live under a rock - GEICO Commercial
HZMMinistries
Uploaded on Mar 24, 2011
Do you live under a rock - GEICO Commercial (HZM #751)