The need for an international sign system was discussed at the first World Deaf Congress in 1951, when the WFD was formed. In the following years, a pidgin began to emerge as the delegates from different language backgrounds communicated with each other, and in 1973, a WFD committee ("the Commission of Unification of Signs") published a standardized vocabulary. They tried to choose the most understandable and inoffensive signs from diverse sign languages to make the language easy to learn. However, there is a dominant influence from American Sign Language and European sign languages, and African and Asian signers find IS considerably more difficult to understand.
A book published by the commission in the early 1970s, Gestuno: International Sign Language of the Deaf, contains a vocabulary list of about 1500 signs. The name "Gestuno" was chosen from Italian, meaning "the unity of sign languages", but the name has fallen out of use in favor of the phrase "International Sign".