تعریف و معنای "dead ringer"

What is the origin of the idiom "dead ringer" and when to use it?

The origin of the idiom "dead ringer" can be traced back to the world of horse racing. In the late 19th century, unscrupulous individuals would attempt to deceive others by substituting a different horse for a favored one in a race. To ensure a successful switch, they would find a horse that closely resembled the favored one in appearance, often referred to as a "ringer." The term "dead" was added to emphasize the remarkable similarity between the two horses. Over time, this idiomatic expression evolved to refer to any person or thing that closely resembles or duplicates another, often to the point of being indistinguishable, whether in physical appearance or other characteristics.