[SE since c.1939, when it was served under that name by the Coney Island Chamber of Commerce to President Franklin D. Roosevelt and his guests, King George VI and Queen Elizabeth of Great Britain and Northern Ireland, the hot dog started life as sl. It prob. comes from heavy-handed mid-19C humour focusing on the supposed use of horse- and dog-meat as sausage filling, a concept that was accentuated by the 1843 scandal concerning the use of dog-meat for human consumption. The image was intensified by the use (c.1860) by German immigrants of Hundewurst, dog sausage, to mean smoked frankfurter sausages (larger sausages were Pferdwurst, horse baloney). The dachshund, of course, is a ‘sausage dog’. The term originated c.1895 at the Yale Club (as well as at Harvard, Cornell and other US ‘Ivy League’ colleges) where lunch wagons were known as ‘dog wagons’ and frankfurters known as ‘hot dogs’]
[late 19C+] (orig. US, alsodoggie, hot pup) a spiced, heated sausage or frankfurter, served on a split roll and trad. garnished with sauerkraut and mustard; thus hotdoggery n., a place selling hot dogs.
2. attrib. use of sense 1.
[1920s+] (orig. US, alsopup) the penis.
[1970s+] (US) a homosexual; also attrib.
[1990s+] (orig. US) a piece of canine excrement.