added to the list, phr. — Green’s Dictionary of Slang

added to the list phr.

[turf jargon; the list was of geldings in training]

castrated.

1873		Sl. Dict.
[1895		C. Crowe Aus. Sl. Dict. 3: Added to the List, in racing parlance, horses added to the geldings].
1923		J. Manchon Le Slang.
1980		Maledicta IV:2 (Winter) 194: A man without testes is referred to as a rascal (from the deer), and if he is ricked, he is said to be added to the list (of steeplechasers in training).