dressed to the nines
The phrase to the nines means perfection. Today, it appears almost exclusively in the form dressed to the nines, but it has not always been paired with dressed and does not exclusively relate to sartorial perfection and the various explanations that discuss nine items of clothing are incorrect. The most likely explanation for the phrase is that nine, in some numerological systems, connotes perfection.
From the Scottish poet William Hamilton of Gilbertfield in his 1719 Epistles to Ramsay:
How to the nines they did content me.
Two lines from Robert Burns, both penned before 1796, use the phrase:
‘Twad please me to the Nine.
Thou paints auld nature to the nines.
The form with dressed appears in the latter half of the 19th century. From Thomas Hardy’s 1876 The Hand of Ethelberta:
When she’s dressed up to the nines for some grand party.
It is sometimes said that the nine in the phrase is a corruption of eyne, the Old English word for eyes. But the phrase appears too late for this to be likely.
(Source: Oxford English Dictionary, New Edition)
Copyright 1997-2017, by David Wilton