I've been reading Betty Smith's A Tree Grows in Brooklyn, and I came across several uses of the word "dockle", usually in the context of light teasing. While I can find some small evidence online of its usage elsewhere, I can't find any actual explanation of its etymology or meaning. The book is set in a lower-class borough of Brooklyn in the early 1900's, if that helps.
From "A Tree Grows In Brooklyn " by Betty Smith:
When none came, she taunted: "Why don't you bust out crying, you dockle?
The following etymological dictionary says it means "doll" which is probably used in the book as a mocking term:
- Frisian dok, G. docke ; a little bundle as of thread, a wisp of straw, also a doll ; Swabian dockle, a doll ; dokheln, to play with a doll.
A dictionary of English etymology, H. Wedgwood - 1859 - History