Words at Play : Top 10 Rare & Amusing Insults
Definition:
ninny; simpleton, fool
About the word:
The word ninny is probably a shortening and alteration of "an innocent" (with the "n" from "an" getting transferred to the noun) and "hammer" adds punch. Writers who have used the word include J.R.R. Tolkien in the Lord of the Rings trilogy: "You're nowt but a ninnyhammer, Sam Gamgee."