Franz Lisp and all other flavors of LISP were eventually superseded by an ANSI standard for Common Lisp. Historically, SKILL was known as IL. SKILL was a library of IL functions. The name was originally an initialism for Silicon Compiler Interface Language (SCIL), pronounced "SKIL", which then morphed into "SKILL", a plain English word that was easier for everyone to remember.
"IL" was only Interface Language. Although SKILL was used initially to describe the application programming interface (API) rather than the language, the snappier name stuck. The name IL remains a common file extension used for SKILL code .il designating that the code contained in the file has lisp-2 semantics. Another possible file extension is .ils, designating that the content has lisp-1 semantics.
G. Wood and H-F S. Law, "SKILL - An Interactive Procedural Design Environment," Proceedings of Custom Integrated Circuits Conference, 1986, pp. 544–547