The origin of the word comes from Sodom, the town in the bible where all of the men folk did the other men folk...
But before they [the angels] lay down, the men of the city, even the men of Sodom, compassed the house round, both old and young, all the people from every quarter: 5 And they called unto Lot, and said unto him, Where are the men which came in to thee this night? bring them out unto us, that we may know[1] them. 6 And Lot went out at the door unto them, and shut the door after him, 7 And said, I pray you, brethren, do not so wickedly. 8 Behold now, I have two daughters which have not known man; let me, I pray you, bring them out unto you, and do ye to them as is good in your eyes: only unto these men do nothing; for therefore came they under the shadow of my roof. 9 And they said, Stand back. And they said again, This one fellow came in to sojourn, and he will needs be a judge: now will we deal worse with thee, than with them. And they pressed sore upon the man, even Lot, and came near to break the door. 10 But the men put forth their hand, and pulled Lot into the house to them, and shut to the door. 11 And they smote the men that were at the door of the house with blindness, both small and great: so that they wearied themselves to find the door.
(Genesis 19:4-11, KJV)
The current definition is...
sod⋅om⋅y   /ˈsɒdəmi/ [sod-uh-mee]
–noun 1. anal or oral copulation with a member of the opposite sex.
2. copulation with a member of the same sex.
Nothing at all about bunnies. I think that even the gayest gay guy would have problems jambing a bunnie up his no no.