where does the term dead end come from
Dead end (street) The expression cul-de-sac comes from French, where it originally meant "bottom of the sack".[44] It was first used in English in anatomy (since 1738). It was used for dead-end streets since 1800 in English (since the 14th century in French).[45] The often heard erroneous folk etymology "arse/ass [buttocks] of the sack" is based on the modern meaning of cul in French, Catalan, and Occitan, but cul doesn't have that meaning in cul-de-sac, which is still used to refer to dead ends in modern French although the terms impasse and voie sans issue are more common in modern French.
Extinction In biology, extinction is the termination of an organism or of a group of organisms (taxon), normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point. Because a species' potential range may be very large, determining this moment is difficult, and is usually done retrospectively. This difficulty leads to phenomena such as Lazarus taxa, where a species presumed extinct abruptly "reappears" (typically in the fossil record) after a period of apparent absence.