“It’s not who you know, it’s whom you know”

“It’s not what you know, but who you know” is an old saying. A jocular take on the saying is:
 
“It’s not who you know, it’s whom you know.”
 
The “whom you know” correction was popularized by the “Dear Abby” newspaper advice column by Abigail Van Buren (a pen name). “DEAR COLLEGE BRED: It isn’t even WHO you know—it’s WHOM you know” appeared in a December 1956 column. “It’s neither. It’s whom you know” appeared in a 1966 column and an almost identical 1977 column.
       
   
18 December 1956, Boston (MA) Daily Record, “Dear Abby” by Abigail Van Buren, pg. 22, col. 5:
DEAR ABBY: I have a college education, am neat and attractive but I am getting nowhere fast. I am beginning to think it isn’t WHAT you know it’s WHO you know.
COLLEGE BRED
 
DEAR COLLEGE BRED: It isn’t even WHO you know—it’s WHOM you know.
 
21 April 1966, The Plain Dealer (Cleveland, OH), “Dear Abby” by Abigail Van Buren, pg. 51, col. 2:
Dear Abby:
I would like a straight answer. In order for a person to get places in this world, is it what you know or who you know?
J. B. in K. C.
 
Dear J. B.:
It’s neither. It’s whom you know.
   
17 March 1976, Arkansas Gazette (Little Rock, AR), “Grin and Bear It” comic strip by Lichty & Wagner, pg. 18B, col. 4:
(Teacher/administrator to a student at a teachers’ college.—ed.)
“Remember, Melvin, to get ahead in the teaching profession it’s not whom you know, it’s whom you know!”
 
19 April 1977, Greensboro (NC) Record, “Dear Abby” by Abigail Van Buren, pg. A11, col. 2:
Dear Abby: I would like a straight answer. In order for a person to get places in this world, is it WHAT you know or WHO you kno>—D. C. in Tulsa.
 
DEAR D.C.: It’s neither. It’s WHOM you know.
 
Google Groups: comp.graphics
anti-aliasing
.(JavaScript must be enabled to view this email address)
2/11/87
(...)
* ARPA: .(JavaScript must be enabled to view this email address)  *  It’s not who you know,  *
* UUCP: mit-eddie!mit-amt!gorin       *  it’s whom you know     *
   
Google Books
Bottom Lines:
The Golden Rules for Executive Success
By Murray Fisher
Los Angeles, CA: General Publishing Group
1994
Pg. 141:
It’s not who you know, it’s whom you know.
 
Google Groups: sci.classics
SUBJUNCTIVE?!
,i>Moiner
3/23/96
(...)
Well, we who are literate tend to use it when the relative pronoun is in the objective case.
 
Remember, it’s not who you know, it’s whom you know.
 
Google Groups: alt.talk.royalty
funeral
Jim Dawes
9/1/97
(...)
It’s not who you know; it’s whom you know.
     
Google Books
Sleeping Dogs Don’t Lay:
Practical Advice For The Grammatically Challenged
By Richard Lederer and Richard Dowis
New York, NY: St. Martin’s Press
1999
Pg. 8
Remember: it’s not who you know; it’s whom you know.
 
Twitter
Twila Marie
‏@twila_zoned
It’s not who you know, it’s whom you know.
8:17 PM - 24 May 2007
   
Google Books
The Mammoth Book of One-Liners
By Geoff Tibballs
London: Constable & Robinson Ltd
2012
Pg. ?:
It’s not who you know, it’s whom you know.