John Ousterhout traces the evolution and unexpected success of the Tcl and Tk scripting languages. The idea for Tcl came from the need for a better command language for integrated circuits design tools. Ousterhout wanted to create a language that was extensible, simple, and could integrate different application features. Tk, on the other hand, was created as a set of GUI components that could be integrated using Tcl as a scripting language. The popularity of Tcl and Tk grew rapidly in the early 1990s due to their simplicity and usefulness in creating graphical user interfaces. The Tcl community formed around the language, contributing powerful extensions and providing support for new users. Ousterhout eventually left Berkeley for Sun Microsystems, where he continued to improve Tcl and Tk with a larger team. In 1998, he founded Scriptics, a startup focused on Tcl, and later renamed it Ajuba Solutions. The transition to a broader group of developers not tied to any organization led to the formation of the Tcl Core Team.
https://www.tcl.tk/about/history.html