Probably the line of origin for "kickboxing" is
Late 1950's-Early 1960's: Cross-rules fights between Oyama dojo karateka (later known as kyokushin) and muay thai stylists start off. Karateka who've lost to muay thai fighters (most notably Kurosaki, who later founded Mejiro gym) feel the need to adapt to a full contact ruleset with a wider array of tecniques
Late 1960's: The All Japan Kickboxing Association is formed as an organization doing muay-thai like fights (i.e. full contact, elbows, clinch). The word "kickboxing" is coined by Noguchi Osamu
1960-1970's: Kickboxing becomes a mainstream sensation in Japan with tens of millions tuning in to watch the fights of Sawamura (another former karateka who lost vs. muay thai). Incidentally Sawamura has a
pokemon named after him
Early 1970's: Dutch martial artists who studied in Japan--Jan Plass-who studied under Kurosaki and later founded the Dutch Mejiro gym--and Thom Harinck--who was a uchideshi in Japan and also learned of MT seperately--form the Dutch Kickboxing Association (I think this is the start of no-elbow KB, but not sure)
Mid 1980's: Kickboxing in Japan fragments as the All Japan splinters (the largest portion which became All Japan Kick Federation, which then in turn splintered). Dutch KB thrives
1993: K-1 is started as a sort of modified full contact karate tournament. No elbow rules are adopted
Late 90's: K-1 becomes a mainstream success, no-elbow rules are widely adopted in international competition
Late 2000's: K-1 starts expanding in to the lower weight classes. No elbow rules start becoming more frequent even in Japan
Its odd to me that westerners associate "kickboxing" with K-1 rules. In Japan (where the term KB originated), kickboxers despise K-1 fighters.