Dead ringer is an idiom in English. It means an exact duplicate or 100% duplicate with implications of dishonesty. The term derives from late nineteenth-century horseracing slang for a horse presented under a false name and pedigree. The "ringer" is a horse substituted for another of similar appearance in order to defraud the bookies.
So, that's ringer; what about dead? Dead, in the sense of lifeless, is so commonly used that we tend to ignore its other meanings. The meaning that is relevant here is exact or precise. This is demonstrated in many phrases; 'dead shot', 'dead center', 'dead heat', etc. So, 'dead ringer' is literally the same as 'exact duplicate'.
The term is sometimes implausibly said to derive, like ‘saved by the bell’, from a custom of providing a cord in coffins for someone who has been buried alive to ring a bell to call for help.
This dead ringer derives its name from a more modern meaning.
Please BYOP and replace the container in the position it was found.
FTF claims bragging rights. Congrats to pcl_el_hefe for the {*FTF*}