let us all go to the 9's...

Numerous attempts have been made to associate the number nine with clothing and so to explain the phrase's derivation. One theory has it that tailors used nine yards of material to make a suit (or according to some authors, a shirt). The more material you had the more status, although nine yards seems generous even for a fop. Another commonly repeated explanation comes from the exquisitely smart uniforms of the 99th (Lanarkshire) Regiment of Foot, which was raised in 1824. The problem with these explanations is that they come with no evidence to support them, apart from a reference to the number nine (or 99, which seems to be stretching the cloth rather thinly). The regiment was in business in the early 19th century, which is at least the right sort of date for a phrase that became widely used in the middle of that century.

What counts against the above explanations, and indeed against any of the supposed explanations that attempt to link the number nine to some property of clothing, is the prior use of the shorter phrase 'to the nine' or 'to the nines', which was used to indicate perfection, the highest standards.