The expression “dead as a Dodo” means unquestionably dead or obsolete. It is so used because Dodo is a well-known icon of extinction. Dodo was a flightless bird that was endemic to the island of Mauritius. It was last sighted in 1662 and was declared extinct by the end of the 17th century.
Dodo received widespread recognition from its role in the story of Alice in Wonderland and has since then been frequently used in popular culture. The exact appearance of Dodo remains a mystery because it can be gauged by only paintings and written accounts from the 17th century and they vary considerably. Sub-fossil remains show the Dodo was about one 1 metre (3.3 feet) tall and may have weighed 10–18 kg.
The first recorded mention of the Dodo was by Dutch sailors in 1598. In the following years it was preyed upon by sailors and their domesticated animals, leading to its extinction by the end of the 17th century. Thus Dodo became extinct within only about a century of its discovery and this highlighted the previously unrecognised problem of human involvement in the disappearance of an entire species.
The Dodo is often used as an icon in Mauritius. Its closest living relative is the Nicobar Pigeon.