"Hinny is most certainly not a deravation of honey."

I think what folk are maybe missing here is that this song seems to have both words in the lyric and like you say they have different meanings.

This link of Judy Dinning has her sing "Where is my boatman, my bonnie hinny" and she wants the boatman to ferry her over the Tyne "to her honey"

http://www.youtube.com/watch?v=dTpBlgDhv6o