When she first started writing detective fiction, Agatha Christie (or her publisher) tended to give the stories titles that were self-explanatory: The Mysterious Affair at Styles, The Murder on the Links, The Murder of Roger Ackroyd, The Murder at the Vicarage and so on.  

As her confidence (and popularity) grew, and she gained more control over the publication of her work, Swigatha started to use fancier titles. The first such was ‘Sing a Song of Sixpence’, a short story included in the Listerdale Mystery collection in 1934. Time and again over the next twenty years she would mine nursery rhymes (and Sing a Song of Sixpence) for her titles, sometimes to witless effect as she tried to manipulate her plots to match the lyrics.

Swigatha had always included liberal amounts of quotation from English literature in her text. Beginning with Sad Cypress in 1940, she started to turn to it for her titles; eventually it would be Shakespeare, Tennyson and the King James Bible that would be quoted on her front pages, replacing the nursery completely.

NURSERY RHYMES

Sing a Song of Sixpence (from The Listerdale Mystery)
A Pocketful of Rye
Four and Twenty Blackbirds (from The Adventure of the Christmas Pudding)
The first three lines of ‘Sing a Song of Sixpence’ provided three titles for Swigatha – two for short stories and one, A Pocket Full of Rye, that gave the author the opportunity to have a riot with the book’s plot as she makes it follow the verses of the eccentric rhyme that inspired it.

And Then There Were None
When attitudes as to what kind of language was and was not acceptable took a turn for the better in the UK, around the middle of the 1980s, a new title was required for Ten Little N*****s, and it was found in the rhyme’s final line, which had in any case been the title used when the book was first published in the US. It is a great title for the book, even if gives away the ending somewhat.

One Two Buckle My Shoe
Each of the chapters contains a line from this children’s counting song as Swigatha tries to squeeze her plot into it.

Five Little Pigs
This is a great story, and there are five protagonists, but the attempt to fit each of them in to the role of ‘This Little Piggy’ doesn’t quite succeed: for example, a girl who survives being disfigured by her sister as a child to become a renowned scholar is described as the little pig who cried ‘wee! wee!’ all the way home.

Crooked House
From ‘There was a Crooked Man….’ and a very appropriate title it is too!

Mrs McGinty’s Dead
A character called Mrs McGinty dies.

Hickory Dickory Dock
A title based on the name of the street where the killings take place and nothing else. The formula was getting tired by now, and thankfully Swigatha realised it – this was the last use of a nursery rhyme as plot device.

How Does Your Garden Grow
Mary Mary quite contrary
How does your garden grow?
With silver bells and cockle shells
And pretty maids all in a row

Poirot duly finds a clue in the shells in a garden bed. Published as one of Poirot’s Early Cases in 1974 but written decades before.

QUOTATIONS FROM LITERATURE

Come, Tell Me How You Live
The title of Agatha Christie’s memoirs of her trips to Syria and Iraq, with her archaeologist husband Max Mallowan, this line is taken from Alice Through the Looking Glass, by Lewis Caroll. Here is the full verse:

I shook him well from side to side
Until his face was blue:
‘Come tell me how you live,’ I cried,
‘And what it is you do!’

She uses the line in a poem at the start ‘with apologies to Lewis Carroll’.

Sad Cypress
Taken from Twelfth Night by William Shakespeare. The clown Feste’s song Come away. come away, death, and in sad cypress let me be laid … is quoted in full at the start. A good choice for a story that has been described as ‘elegiac’.

The Hollow
From Maud, a ‘monodrama’ by Alfred Tennyson. The opening lines are:
I hate the dreadful hollow behind the little wood,
Its lips in the field above are dabbled with blood-red heath,
The red-ribb’d ledges drip with a silent horror of blood,
And Echo there, whatever is ask’d her, answers ‘Death.’

This verse is quoted by Poirot in the text. The obvious connection is the name of the house where death occurs, although one of the characters considers that the man killed is more alive than anyone else – they are all but ‘Echoes’.

Taken at the Flood
From Julius Caesar, by Shakespeare. Brutus to Cassius: There is a tide in the affairs of man which, taken at the flood, leads on to fortune … This a very appropriate title for a story about someone who sees an outlandish opportunity and seizes it, with no regard for the consequences.

Evil Under the Sun
From the Bible (the Book of Ecclesiastes):  I have seen another evil under the sun, and it weighs heavily on mankind.

The same thought occurs to Poirot and the Rev Stephen Lane as they watch people sunbathing – that there is evil everywhere under the sun; it is especially manifest when Poirot is around.

N or M?
This title comes from the Catechism in the Book of Common Prayer which asks, “What is your Christian name? Answer n. or m.”  The original Latin version had “nomen vel nomina”, meaning “name or names”; this was shortened to ‘n or nn’ for the English language version. By a mistake in the transcription  that was not picked up, ‘nn’ came to be represented by “m”: hence ‘n or m’.

The Brazilian version of this title is ‘M ou N?’, oddly.

The Moving Finger
From The Rubaiyat of Omar Khayyam: The moving finger writes, and having writ, moves on. A great title for a book – what is done cannot be undone – but in this case the writing concerned is in the form of poisonous pen letters referring to things which had NOT happened.

The Pale Horse
From the Bible (the Book of Revelation):  And I looked, and behold a pale horse: and his name that sat on him was Death, and Hell followed with him. In the book, it is the name of a (sinister) pub.

The Mirror Crack’d from Side to Side
From The Lady of Shalott by Tennyson:
Out flew the web and floated wide
The mirror crack’d from side to side:
“The curse is come upon me,” cried
The Lady of Shalott.

An absolutely inspired choice of title, perfectly fitting the crucial moment in the story, as described by Mrs Bantry to Jane Marple.

Endless Night
From Songs of Experience by William Blake:
Every Night and every Morn
Some to Misery are born
Every Morn and every Night
Some are born to Sweet Delight,
Some are born to Sweet Delight
Some are born to Endless Night.

This story is about a person whom even the mother who bore him knew would come to no good.

By the Pricking of My Thumbs
From Macbeth by Shakespeare: 

Second Witch: By the pricking of my thumbs, something wicked this way comes.

A ‘pricking of the thumbs’ is the witch’s reaction, similar to a shudder, at the approach of Macbeth. It’s also how Tuppence feels when she first meets the person who proves to be the murderer, though she misreads the cause.

It is also how I feel when I watch the start of another Walliams Tommy and Tuppence adaptation on BBC.

Postern of Fate
From the Gates of Damascus by James Ellroy Flecker:
Four great gates has the city of Damascus … Postern of Fate, the Desert Gate, Disaster’s Cavern, Fort of Fear...

Difficult to know why this title was chosen, but then again everything about this book is difficult, including reading it.

In a Glass Darkly
From the Bible: St Paul’s First Letter to the Corinthians.

The King James version is the most common one: For now we see through a glass darkly …  but there are many translations, and this is one of them. This story was published in Miss Marple’s Final Cases (even though she is not in it) after Agatha Christie’s death.

While the Light Lasts
Not sure where this comes from – it was used in memoriam of quite a few British and Commonwealth soldiers who died in WW1. Many online websites say it comes from a poem by Lord Tennyson, but I have not been able to trace it:
While the light lasts
I shall remember
And in the darkness
I shall not forget

This was the title story of another collection published posthumously. In it, a widow had used this quote in the obituary to her husband, presumed killed in WW1. He returns, under the alias of ‘Enoch Arden’, to find her married again. Enoch Arden is the name of an actual Tennyson poem, one that also features in Taken at the Flood.