Tcl, Fossil and SQLite share an interesting history. SQLite started as a Tcl extension and the SQLite maintain Dr Richard Hipp is part of the Tcl Core Team as well. Fossil started out as a version control for SQLite development by Dr Richard Hipp as well, and might have influenced the Tcl development as well.
Source: https://www.sqlite.org/tclsqlite.html https://wiki.tcl-lang.org/page/D.+Richard+Hipp