Blockheads

• Simple souls process number two, having spent a penny
• Dumb bunnies
• Chuckleheads
• Numbers kept outside part of the UK, stupid folk

Wiktionary Word definitions in Wiktionary
n. (ninny English)

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Ninny \Nin"ny\, n.; pl. Ninnies . [Cf. It. ninno, ninna, a baby, Sp. ni[~n]o, ni[~n]a, child, infant, It. ninna, ninna nanna, lullably, prob. fr. ni, na, as used in singing a child to sleep.] A fool; a simpleton. --Shak.