Not a dicky-bird
Not a sound; not an utterance.
A 'dicky-bird' might be of uncertain spelling - it is variously spelled 'dicky-bird', 'dickey-bird', 'dickybird', 'dickeybird' and, when referring to the retired English cricket umpire, 'Dickie Bird'. The country of origin isn't at all uncertain; 'dicky-birds' are unequivocally English. The term dates from at least the 18th century, when it appeared in the London Evening News, May 1766, as the title of a story they intended shortly to publish:
"The Swan and the Dickey-bird: A fable - shall be inserted in our next"
At that time 'dickey-bird' was a generic nursery term for the small, chirruping birds often found in the English countryside and features in the well-known nursery rhyme Two Little Dicky Birds. The rhyme is usually accompanied by wiggling index-finger gestures, to represent the birds:
Two little dicky birds,
Sitting on a wall;
One named Peter,
One named Paul.
The rhyme was adapted from the earlier 'Two Little Blackbirds', which was first published in London in the first book of nursery rhymes, Mother Goose's Melody, circa 1765:
There were two blackbirds
Sat upon a hill,
The one was nam'd Jack,
The other nam'd Gill.
The 'not a dicky-bird' phrase indirectly derives from the tweeting sounds made by the birds. 'Dicky-birds' became established as a Cockney Rhyming Slang term for 'words', in the mid 20th century. The first record of it in print is in the 1932 'P. P.' Rhyming Slang:
" Word... Dicky bird."
So, 'not a dicky-bird' means 'not a word', i.e. silence, especially in the context where a spoken or written word might have been expected - for example, 'Jack said he would write, but I haven't heard a dicky-bird from him for weeks'.