The trash can icon is one of the oldest digital GUI icons. It was featured in the interface of the Xerox Alto in 1973 and has established its position as the standard symbol for deleting files. The metaphor of a trash can is accurate, as the files are temporarily maintained until the trash can is actually emptied.
Over time the icon has evolved from the classic cartoon style garbage bin of e.g. the Xerox Star which is featured here, to a more sophisticated trash can, which you would more likely find in any office. The icon usually features different states depending on whether it contains files or not.
Xerox Alto 1973.