Green’s Dictionary of Slang

yeknod n.

also jerk-nod

[backsl.]

a donkey.

1859		Hotten Dict. of Modern Sl. etc. 131: YEKNOD, or jerk-nod, a donkey.
1864, 1867, 1870		Hotten Sl. Dict. [as cit. 1859].
1873		Sl. Dict.