"Similarly (according to) other physicians the spleen (is) the receptacle of melancholy as the gall bladder of gall; wherefore the spleen causes one to laugh"
William Harvey,
Lectures on the Whole of Anatomy(1653)
Have you ever wondered what a good belly laugh has to do with getting sewn up? Did you ever become aware while giggling really hard how your ribs hurt? That common cramping or stabbing feeling suggests the pain feels like getting stuck in the ribs by something sharp. Many people will say that something was so funny it left them “in stitches."

The answer lies in the etymology of stitches, which developed from a Germanic word stikiz meaning sting or prick, as in "to stick or jab with a sharp point." Old English picked it up from Old English stice from there it became the modern day word stitch. Add the preposition in and it creates the informal idiomatic phrase in stitches describing doubling over until you sides aches. Oxford English Dictionary explains that as early as the year 1000 stitch was used to indicate “an acute spasmodic pain in the side, as if stabbed.” Most of today’s experts say that stretching the ligaments that attach the liver to the diaphragm probably causes these side stitches and laughing uncontrollably may well be the reason for the sharp pain.

One interesting clue about the evolution of the phrase comes from William Shakespeare. Written in the middle of his career, most critics consider Twelfth Night to be one of his greatest comedies about illusion, deception and disguises. One article from The Bard on the Beach explains where Shakespeare may have developed his story lines:

As is the case with most of Shakespeare's plays, the story of Twelfth Night is derived from other sources. In particular, Shakespeare seems to have consulted an Italian play from the 1530s entitled Gl'Ingannati, which features twins who are mistaken for each other and contains a version of the Viola-Olivia-Orsino love triangle in Twelfth Night. He also seems to have made use of a 1581 English story entitled "Apollonius and Silla," by Barnabe Riche, which mirrors the plot of Twelfth Night up to a point, with a shipwreck, a pair of twins, and a woman disguised as a man. A number of sources have been suggested for the Malvolio subplot, but none of them is very convincing. Sir Toby, Maria, and the luckless steward seem to have sprung largely from Shakespeare's own imagination.
Over a 25-year period, Shakespeare wrote 37 plays, 154 sonnets and two narrative poems, which are quoted and closly studied extending his influence into everyday language, as many of his phrases have become common sayings. The `twelfth night' is on January 6th or twelve days after Christmas. In the many Christian church calendars the celebration is known in as the Feast of The Epiphany. A number of sources say that the play was commissioned by Queen Elizabeth I to be performed on Twelfth Night, because she was expecting a visit by the young Don Virginio Orsino, Duke of Bracciano.

It’s in Act 3 Scene 2 when the three characters which sprang from Shakespeare’s imagination Malvolio, Sir Toby and Maria make up the scene. Olivia is the main character and most likely modeled on the character of Queen Elizabeth. Not only is a “Duke” pursuing her hand among many others Malvolio, Countess Olivia's snobbish steward is secretly in love with her. Knowing this, Olivia’s maid Maria has written him a love letter disguised in her mistress' handwriting, telling him to beam smiles at Olivia frequently, wear yellow stockings, and dress cross-gartered – all of which Olivia detests. Malvolio calls on Olivia, dressed and performing in the manner suggested by the correspondence in great expectations of romantic success....

==Enter Maria
Sir Toby Belch
Look, where the youngest wren of nine comes.
If you desire the spleen, and will laugh yourself
into stitches, follow me. Yond gull Malvolio is
turned heathen, a very renegado; for there is no
Christian, that means to be saved by believing
rightly, can ever believe such impossible passages
of grossness. He's in yellow stockings.
Sir Toby Belch
And cross-gartered?
Most villanously; like a pedant that keeps a school
i' the church. I have dogged him, like his
murderer. He does obey every point of the letter
that I dropped to betray him: he does smile his
face into more lines than is in the new map with the
augmentation of the Indies: you have not seen such
a thing as 'tis. I can hardly forbear hurling things
at him. I know my lady will strike him: if she do,
he'll smile and take't for a great favour.
However, the entire group assumes he has gone mad and, at Maria's proposal, poor Malvolio is locked away in a dark room. Here are some interesting excerpts from that may give those who haven’t seen the play an idea of what the play is about. They’re from William Hazlitt's Characters of Shakespear's Plays published in 1818.
Twelfth Night is justly considered to be one of the most delightful of Shakespeare’s comedies....It aims at the ludicrous rather than the ridiculous. It makes us laugh at the follies of mankind, not despise them, and still less bear any ill will towards them.... the same house is big enough to hold Malvolio, the Countess, Maria, (and) Sir Toby...in a word, the best turn is given to everything, instead of the worst. There is a constant infusion of the romantic and enthusiastic, in proportion as the characters are natural and sincere. ...We have a friendship for Sir Toby…. a sneaking kindness for Maria and her rogueries; we feel a regard for Malvolio, and sympathize with his gravity, his smiles, his cross garters, his yellow stockings, and imprisonment in the stocks.
Even though the idiom in stitches dates from around 1930, Shakespeare uses what is most likely the earliest form of the expression in his play when Maria says, “If you desire the spleen, and will laugh yourself into stitches, follow me.” Historians say the play was probably written between 1599 and 1601. In Shakespeare's day the spleen was thought to be repository of the most noxious substance of the body black bile and its job was to prevent the onset of melancholia by containing the bodily fluid that produced this mental state. Hence the ability to laugh was a sign that the spleen was working well.


The American Heritage® Dictionary of Idioms, 1997.

Bard on the Beach:

Garrison, Webb B., Why You Say It, Rutledge Hill Press; (November 1992)

Public domain text and some information taken from Sparknotes Online Study Guides:

CST Approved.