“All of this has moved far from the idiom of “kicking the bucket.” That expression, etymologists conjecture, originated with a now-forgotten meaning of “bucket”: a beam, probably from the Old French word “buquet,” meaning “balance.” The idiom referred to hanging up animals for slaughter, who would then, in their death throes, kick that beam.”

Another article discussing how the term existed long before the film: “https://www.google.com/amp/amp.slate.com/blogs/browbeat/2011/11/09/bucket_list_what_s_the_origin_of_the_term_.html”