1. uncertain...Bk1847 Eng. dial.
2. stupid, foolish, weak-minded, childish ...Bk1865 Eng. dial.
3. of small account ...Bk1865 Eng. dial.
a silly, weak-minded, or foolish person ...1823 Eng. dial.
from ninny (n. a fool, a simpleton) + nonny (Eng. dial. variant of 'ninny')
FIRST DOCUMENTED USE
1823 - see EXAMPLE below
"...Still, still he flogged, and cried, "'tis nought to You,
"Go heal your smarting wounds at Nature - do."
"Yes, do, my pretty little ninny nonny,
"And when I've done, I'll whip your brother Johnny."
Still - still he flogged - till worn - outwearied quite -
Scarificator left him in sad plight...."
From: Visions of Taste: A Satire.
By David Douglas, 1823
Part I. Sect. II
Vision I, The School of Poetry