Purportedly old-fashioned slang

[Jesse Sheidlower]

I was visiting someone at a fancy beach resort in Palm
Beach. There's a group of teenage girls there, all pose-y in
small bikinis and so forth, and a group of teenage boys in a
clump, not sure what to do.

This one boy, shirtless and muscled, is walking up to the
girls, and another boy yells to him, "Josh, put your shirt on,
you ninny!"

I thought to myself, "_ninny_?"

After a pause, another boy says, in this incredulous voice,
"_ninny_?"

I almost fell over laughing.

Just a report from the front.

Jesse Sheidlower
OED