I thought the exact same thing when I saw the movie. Couldn't get past it. I always pictured it spelled as "dobbie" for no good reason. Maybe it seemed a little less offensive spelled that way. And I remember it used in the singular form (as in "Laurel just deposited a dobbie in the pool").

I think my mother invented the word, but you'll have to check with her as to it's etymology. As to the meaning, it's better left unpublished on this here blog.