“My word is my bond” (Dictum Meum Pactum in Latin) became the motto of the London Stock Exchange in 1923 and the Security Traders Association in 1934. “My word is my bond” is an old saying that has been cited in print since at least 1748.
 
The American rapper Ice-T released “My word is bond” is 1988, and the saying became popular with other hip hop artists. “Word is bond” was released by House of Pain in 1994 and 5th Ward Boyz in 2003.
 
 
Wikipedia: London Stock Exchange 
The London Stock Exchange is a stock exchange located in the City of London in the United Kingdom. As of December 2011, the Exchange had a market capitalisation of US$3.266 trillion (short scale), making it the fourth-largest stock exchange in the world by this measurement (and the largest in Europe). The Exchange was founded in 1801 and its current premises are situated in Paternoster Square close to St Paul’s Cathedral in the City of London. The Exchange is part of the London Stock Exchange Group.
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In 1923 the Exchange received its own Coat of Arms, with the motto “Dictum Meum Pactum”, My Word is My Bond.
 
London Stock Exchange—Our History
1923
The Exchange receives its own Coat of Arms, with the motto “Dictum Meum Pactum” (My Word is My Bond).
 
Security Traders Association—Who is STA
STA is the leading trade organization for individual professionals in the securities industry that works to improve the ethics, business standards and working environment for its members. STA is comprised of 26 Affiliate organizations, nationally and internationally, with a total of 4,200 professional trade industry members who are engaged in the buying, selling and trading of securities.
 
The Security Traders Association is committed to promoting the interests of its members throughout the global financial markets, providing representation of these interests in the legislative, regulatory and technological processes, while fostering goodwill and high standards of integrity in accord with the Association’s founding principle, Dictum Meum Pactum – ” My word is my bond “.
   
Google Books
The Congress of the Beasts
A Farce of Two Acts
By John James Heidegger
London: Printed for W. Webb
1748
Pg. 20:
Fox. My Word is my Bond.
 
Google Books
The Comic Theatre:
Being a Free Translation of All the Best French Comedies, Volume 4
By Samuel Foote
London: Printed by Dryden Leach
1762
Pg. 144 (The Amorous Quarrel):
METAPHRASTUS.
My word is my bond.
 
16 June 1840, Nantucket (MA) Inquirer, “Reflections of a Reformed Drunkard,” pg. 1, col. 3:
Then could I drink with a clear conscience—but I signed the pledge, and my word is my bond.
 
OCLC WorldCat record
“My word is my bond”: the Stock Exchange, some questions and answers.
Author: Stock Exchange (London, England)
Publisher: London, Stock Exchange [1951]
Edition/Format: Book : English
 
28 February 1954, Sunday World-herald (Omaha, NE), pg. 2-F, col. 3:
“My word is my bond,” is the motto of the market.
 
12 March 1961, San Diego (CA) Union, “London Stock Market Keeps Ties With Past,” pg. A51, col. 5:
Once a deal or “bargain” has been agreed to verbally, it is market down in notebooks of broker and jobber. No formal documents are signed, for on the exchange a man’s word is his bond. That phrase is the House’s proud motto: “Dictum Meum Pactum.”
 
7 September 1969, Seattle (WA) Times, “Split-Second Deciders” by Boyd Burchard, pg. 35, col. 5:
Credo of the National Securities Traders Association, organized in 1939 under an act of Congress as a self-regulatory professional association for the protection of the public, is “dictum meum pactum—my word is my bond.”
 
OCLC WorldCat record
The iceberg ...
Author: Ice-T, (Musician)
Publisher: [New York] : Sire, 1988.
Edition/Format: Music CD : CD audio : Rock music : English
Contents: My word is bond
 
OCLC WorldCat record
Same as it ever was
Author: House of Pain (Musical group)
Publisher: New York : Tommy Boy, 1994.
Edition/Format: Music CD : CD audio : English
Contents: Word is bond (4:02)—
 
OCLC WorldCat record 
Word is bond
Author: 5th Ward Boyz (Musical group)
Publisher: Houston, Tex. : Underground Recordz, p©2003.
Edition/Format: Music CD : CD audio : English
 
Urban Dictionary
word is bond
Quite possibly the most popular saying among the members of the Wu-Tang Clan
That nigga Shamiek just got bust in his head two times, guy. Word is bond.
by edd0 Aug 29, 2003
 
Urban Dictionary
my word is my bond
It’s a maritime brokers’ motto. Since 1801 the motto of the London Stock Exchange (in Latin “dictum meum pactum”) where bargains are made with no exchange of documents and no written pledges being given.
“My word is my bond” as brokers say (or “my word, my bond!”)
by dalilah Jun 10, 2006
 
OCLC WorldCat record
My word is my bond : voices from inside the Chicago Board of Trade
Author: Arlene Michlin Bronstein; CME Group.
Publisher: Hoboken, N.J. : John Wiley & Sons, ©2008.
Edition/Format: Book : Biography : English
Database: WorldCat
Summary: My Word Is My Bond is an intimate look into the Chicago Board of Trade. It contains a collection of interviews with twenty-one of the most influential members of that established bastion of auction markets. The author explores each participant in-depth and takes you to a never- before-seen place on the exchange floor-and beyond.