Nip and tuck
A close result in a race or contest. More recently, the name of a cosmetic surgery procedure.
The 'close result' meaning of this phrase originated in the 19th century. It is easy to see why it was later appropriated as the name of the minor cosmetic surgery 'skin-tightenning'. Nipping and tucking are what me might imagine being done in such a procedure. The name began being used in the 1970s and the earliest reference I can find to it in that context is from The Lethbridge Herald, January 1974:
It's top-to-toe cosmetic surgery [for Liz Taylor's character] at an expensive European clinic to take the sag out of a failing marriage. Liz emerges porcelain pretty, accompanied by Keith Baxter playing Roddy McDowell (he's had a bit of the nip and tuck at the clinic too).
The earlier usage is a little more difficult to understand as the connections between both words 'nip' and 'tuck' and the 'close result' meaning of the phrase aren't easy to see. There is an earlier expression 'rip and tuck'. This has a different meaning - something akin to 'fast and loose', but it is hard to imagine that the two phrases are unrelated. 'Rip and tuck' is first found in James Kirke Paulding's Westward ho!, 1832:
"There we were at rip and tuck, up one tree and down another."
The first known usage of 'nip and tuck' comes from an 1845 edition of The American Whig Review:
"The boys used to say, it was nip and tuck between Jack... and Castro, who would do the most foolhardy things."
I have found the expression in print a little earlier than that, although just as a name rather than an expression that implies the 'close result' meaning. That is is the Milwaukie Sentinel, September 1843. The paper reported on the suggestion that various adjoining mineworkings in the Wisconsin goldfields should be merged. One of the sub-fields was call 'Nip and Tuck'.
Why 'nip' and why 'tuck'? There are several meanings of both words but none of them suggests anything that relates directly to any sort of close race or result. The phrase is somewhat similar to 'neck and neck', which has virtually the same meaning. It is possible, although I'd admit, entirely speculative, that 'nip and tuck' is a deliberately garbled version of 'neck and neck'. Apart from that, I'm out of ideas.