When the design of ships sterns changed to a broad shape that had the props fully under the hull rather than more or less exposed beyond the sides of the ship (as seen on Flush-deckers). The term of "Fantail" defined the area of the deck over the props. Specifically for the USN destroyers from about the FARRAGUT class and newer had this new hydro design and the term "fantail" became common, rather than poop deck.
: same as transom ??? any one ?