"A gathering of baboons is called a congress"

“A group of baboons is called a congress” is a “fact” that became popular on the Internet by about 1999. A group of baboons is usually called a “troop” and a large number of baboons is sometimes also called a “tribe.” Politifact (Rhode Island) rated “a congress of baboons” as “PANTS ON FIRE” (absolutely not true) in December 2011.

However, “A Congress of Baboons” was a headline in the Kansas City (MO) Star in 1893. “The council hall stank like a congress of baboons” was cited in a 1971 book. If enough people write “congress of baboons”—and there are plenty of modern citations—the “error” could possibly become standard English.

Wikipedia: List of collective nouns
This is a list of Standard English collective nouns. The large number of collective nouns in English is based on a tradition of venery (words for groups of animals) which arose in the Late Middle Ages.
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baboons troop

(Oxford English Dictionary)
troop, n.
Of animals: A herd, flock, swarm; esp. a group of apes or monkeys.
1587 L. Mascall Bk. Cattell (1596) 237 Fold for sheepe… Make your pennes..in some drie ground, and make also partitions thereinto to receiue small troups of forty or moe.
1604 E. Grimeston tr. J. de Acosta Nat. & Morall Hist. Indies iv. xxxiii. 299 In Peru there is such store of pastures and feelings, as..every man feedes his troupes where he pleaseth.
1719 D. Defoe Life Robinson Crusoe 355 We perceiv’d 2 or 3 Troops of Wolves.

tribe, n.
A number or company of persons or animals; a ‘troop’; in pl., large numbers, ‘flocks’.
1715 Pope Temple of Fame 32 Then came the smallest Tribe I yet had seen, Plain was their Dress, and modest was their Mien.
1820 W. Scoresby Acct. Arctic Regions II. 209 The same tribe of whales were seen in the latitude of 78°.

16 November 1893, Kansas City (MO) Star, pg. 2, col. 2:
A Congress of Baboons.
From Home Life on an Ostrich Farm by A, Martin.
One of our friends traveling on horseback came upon a number of baboons sitting in solemn parliament on some rocks.

Google Books
Down in the Black Gang, and Others;
A Story Collection
By Philip José Farmer
Garden City, NY: Nelson Doubleday
1971
Pg. 79:
Mix swallowed the comment he wanted to make, that the council hall stank like a congress of baboons.

Google Books
What Do You Call a Group of Hippos?: And Other Mammal Groups
By Emma Nathan
Woodbridge, CT: Blackbirch Press
2000
Pg. 4:
A group of baboons is called a congress.

British Comedy Guide
- A group of baboons is called a “Congress”, although the word “Flange” (which originated from the ‘Gerald the Talking Gorilla’ sketch in Not the Nine O’Clock News) is beginning to replace it and is now even being used by some academics as the official word.
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First Broadcast Details
Date: Fri 12th November 2004
Time: 10:30pm
Channel: BBC Four

Google Books
Teachers Resource Book:
Developing Literacy, Book 1
By Diane Henderson/Rosemary Morris
Greenwood, Western Australia: R.I.C.Publications
2007
Pg. 28:
A cluster of antelope
A herd of antelope
A tribe of antelope
A troop of apes
A congress of baboons

Twitter
r. jean roth
‏@jrotem
@foxvox @maryo well anything is better than a congress of baboons http://www.rinkworks.com/words/collective.shtml
Reply Retweet Favorite More
6:59 PM - 31 Oct 08

Twitter
Neil Fitzmaurice
‏@Fitzyfella
@soc_it_to_me_ a flange is a collective
noun, it’s a gathering of Baboons! Why what did you think I meant??
12:18 PM - 7 Jul 11

Urban Dictionary
Congress
Congress usually refers to the national legislative body of a country. However, congress is a term also used for a group of baboons. That there are obvious similarities between these groups should be pretty obvious to most.
Consider a group of Baboons, they are the loudest, most dangerous, most obnoxious, most viciously aggressive and least intelligent of all primates. And what is the proper collective noun for a group of baboons? Believe it or not ....... a Congress!
I guess that pretty much explains the things that come out of Washington!
by rufustherat September 03, 2011

Twitter
Ashutosh Sharma
‏@uber_ash
A gathering of baboons is called - a congress. May be we ought to start a party after a gathering of lions - a Pride… #idea
12:49 AM - 2 Oct 11

Politifact (Rhode Island)
The Truth-O-Meter Says:
Chain email
“What is the proper collective noun for a group of baboons? Believe it or not . . . a Congress!”
Chain email on Saturday, December 10th, 2011 in a message via the Internet
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So we turned to Orin Hargraves, a freelance lexicographer and president of the Dictionary Society of North America. (...) “Apparently someone just made it up,” he said. “It has the ring of truthiness and so people like it. They do behave like the caricature of the baboons, but I think real baboons probably behave a lot better.”

We also turned to two anthropologists who really know baboons.
(...)
Both said the correct term for a group of baboons is a “troop.”
(...)
If someone presents this joke e-mail to you as the truth, tell them they need to step away from the smoke detector because they’ve got Pants On Fire!

Twitter
lisa witham
‏@cheezwitham
@SpeakerBoehner Hey Speaker Boehner did you know a LARGE Gathering of Baboons is called a CONGRESS?Gee I WONDER WHY WHY! It explains A LOT
7:30 AM - 22 Apr 13

Twitter
Simon-Paul Ridgeway
‏@RidgewaySimon
A large number of baboons is called a congress; and a large number of Congressmen are BAFOONS https://www.facebook.com/photo.php?fbid=10151732095762987&set=a.188529682986.126360.85073967986&type=1&theater …
4:41 AM - 25 Oct 13

“A gathering of baboons is called a congress”