“DOTUS” (Dog Of The United States) is a nickname acronym for a dog of the president of the United States. “First dog” is also sometimes used.
   
“Because Clinton’s nickname around the White House is POTUS, short for President of the United States, some said he should call it DOTUS, for Dog of the United States” was printed in the St. Louis (MO) Post-Dispatch (and other newspapers) on December 17, 1997. “DOTUS Dogs Of The United States” was entered in the Urban Dictionary on November 8, 2020. “The Oval Pawffice® [Flag of United States] DOTUS Fans @TheOvalPawffice Pawffice of #COTUS & #DOTUS - the fan page for #Willow and #Commander Biden. Not affiliated with the #WhiteHouse. #FirstCat #FirstDog” joined Twitter in November 2020.
   
A list of the pets of the United States presidents is here.
   
Similar acronyms include “COTUS” (Cat Of The United States), “POTUS” (President Of The United States), “PEOTUS” (President-Elect Of The United States), “FLOTUS” (First Lady Of The United States), “VPOTUS” (Vice President Of The United States), “SCOTUS” (Supreme Court Of The United States), “COTUS” (Constitution Of The United States) and “TOTUS” (Teleprompter Of The United States).
       
     
Newspapers.com
17 December 1997, St. Louis (MO) Post-Dispatch, “Clinton’s new puppy finally has a name; he’s the president’s ‘Buddy,’” pg. A2, col. 3:
Because Clinton’s nickname around the White House is POTUS, short for President of the United States, some said he should call it DOTUS, for Dog of the United States.
 
Google Groups: soc.culture.vietnamese
Tha ho^` ma` cho.n
Le^ Hu+ng
Dec 20, 1997, 3:00:00 AM
(...)
Mo^.t ca’i te^n kha’c cu~ng ra^‘t hay nhu+ng kho^ng d-u+o+.c cho.n: Dotus. Dotus la` vie^‘t ta(‘t cu?a Dog Of The United States.
     
Twitter
Diane Prange
@DianePrange
Should Obama’s dog be named DOTUS (Dog of the United States)
12:17 PM · Jan 29, 2009·Twitter Web Client
 
Newspapers.com
19 April 2009, The News-Star (Monroe, LA), pg. 5B, col. 2:
From DOTUS, top dog of the US
Kevin A. Unter
Columnist
   
Twitter 
Conservatarian
@Conservatarian
Does DOTUS (Dog Of The United States) have a twitter account yet, or a blog? LOL #tcot #tlot
2:02 PM · Apr 15, 2009·Twitter Web Client
 
Twitter 
Kim Insley
@KimInsley
The top dog of the US.  “DOTUS” RT @nbcnightlynews Video: Best of Bo http://bit.ly/H2GD3
9:51 PM · Jun 5, 2009·Twitter Web Client
   
Twitter
PhyllWill
@PhyllisTeachpvw
Replying to @FLOTUS44
@FLOTUS @whitehouse Bo looks good against the background! He the official Dotus- Dog of the US! Lol!
7:26 PM · Jan 27, 2013·Twitter for Android
 
Google Books
Historical Dictionary of the Barack Obama Administration (second Edition)
By Michael J. Pomante II and ‎Scot Schraufnagel
Lanham, MD: Rowman & Littlefield
2018
Pg. 265:
Bo is a Portuguese water hound and has been referred to as the “DOTUS” (Dog of the United States) or the “First Dog.”
 
Urban Dictionary
DOTUS
Dogs Of The United States
German Shepherds Major and Champ will become DOTUS in the White House when Joe Biden is President of the United States
by acnyc November 08, 2020
 
Twitter
The Oval Pawffice® [Flag of United States] DOTUS Fans
@TheOvalPawffice
Pawffice of #COTUS & #DOTUS - the fan page for #Willow and #Commander Biden. Not affiliated with the #WhiteHouse. #FirstCat #FirstDog
Washington, DC theovalpawffice.com Joined November 2020
   
Twitter
Antonette & Marcus
@TheAntonMarcus
Replying to @eggshellfriend
It’s a Twitter account for the Dotus and cotus - dog and Cat of the US. But yeah weird tweet.
4:30 PM · Feb 19, 2021·Twitter for iPhone
 
Twitter
Bobby Hutchinson
@hobbybutchinson
DOTUS? As in Dog of The United States?
Quote Tweet
The Oval Pawffice® Flag of United States DOTUS Fans
@TheOvalPawffice
· Dec 20, 2021
Henlo, frens! My name is #Commander, I’m Major’s new baby brother and I’m so furry happy to be pawrt of the wonderful Biden family. Major told me that I am now a First Dog too, just like him. Isn’t that pawbulous? Wuuf wuuf! - Commander #DOTUS #FirstPuppy
11:39 AM · Dec 21, 2021·Twitter for iPhone