Flibbertigibbet & Co.

A lovely noun that came to us in Middle English,  a Flibbertigibbet is "a silly, scatterbrained, or garrulous person" (AHD).

And now for a nitpicker's definition:

Silly--This adverb originated in Old English as gasælig meaning "blessed." In Middle English a spelling more recognizable developed as seli, silli with a likewise more familiar definition: "blessed, innocent, hapless." Today the word is used to denote something "foolish," "frivolous," or "dazed" (AHD).

Scatterbrained--As a compound this adjective describes someone who is "flighty, thoughtless, or disorganized." The first of its parts, scatter, comes from a possible Middle English "dialectical alteration of OE sceaterian." Brained, the second portion, has its origins in Old English as brægen with the same definition we use today (AHD).

Garrulous--An adjective describing one "given to excessive and often trivial or rambling talk; tiresomely talkative," garrulous' origins are traced to the Latin word for chatter garrire (AHD).