“To the nines” is an idiom meaning “to perfection” or “to the highest degree,” thus, “dressed to the nines” means to dress flamboyantly or smartly.
Several theories link the origin of the phrase to clothing. One has it that tailors used nine yards of material to make a suit. But, however many yards of material might be used, that says nothing about perfection, or the lack of it. Another says it’s related to the 99th Wiltshire Regiment, known as the Nines, which was renowned for its smart appearance.
We can dismiss those explanations, and any others that link the phrase to clothing, because the prior use of the shorter phrase ‘to the nine’ or ‘to the nines,’ meant perfection, the highest standards. That shorter phrase was found in writing in the 1700s, well before ‘dressed to the nines’ was first used, as in this example from the Scottish poet William Hamilton’s Epistle to Ramsay, 1719:
The bonny Lines therein thou sent me,
How to the nines they did content me.
A different theory attributes the phrase to a three-masted sailing ship, each mast having three “yards,” or spars. Under full sail (“at the highest point”), the ship would be using nine sails. This theory is tied in with the phrase “the whole nine yards,” which comes from the same arrangement of sails. There is no evidence whatever that either theory is true.
We seem always to have been fascinated by the number nine itself. Cats have nine lives, and Hell has, it is said, nine levels. The Nine Worthies were characters drawn from Pagan and Jewish history as personifications of chivalry. Also, classical mythology gives us the Nine Muses of Arts and Learning — Clio, Thalia, Erato, Euterpe, Polyhymnia, Calliope, Terpsichore, Urania and Melpomene. In Norse cosmology, the great tree Yggdrasil unites nine worlds.
Nine is also three times three, a symmetry that has long figured in magic and numerology. And nine is, of course, the closest you can get to ten, the “highest degree” in many contexts. So if someone says that you are “dressed to the nines,” you’ve flown as close to the white-hot pinnacle of fashion as it’s advisable to get.
The Poetick Miscellenies of Mr John Rawlett, 1687, appears to be the earliest reference to ‘to the Nine,’ which clearly must be the nine Muses:
Both the Philosopher and Divine,
And Poets most who still make their address
In private to the Nine.
It is quite clear that ‘dressed to the nines’ is merely an extension of ‘to the nines’ and that we could equally well ‘dance to the nines’ or ‘cook to the nines.’