The word "gimlet" used in this sense is first attested in 1928. The most obvious derivation is from the tool for drilling small holes, whose name is also used figuratively to describe something as sharp or piercing. Thus, the cocktail may have been named for its "penetrating" effects on the drinker.
Another theory is that the drink was named after British Royal Navy Surgeon Rear-Admiral Sir Thomas Gimlette KCB (1857-1943), who allegedly introduced this drink as a means of inducing his messmates to take lime juice as an anti-scurvy medication as Limes and other citrus fruit have been used by the Royal Navy for the prevention of scurvy since the mid-18th century.
The gimlet is a cocktail made of gin or vodka and lime juice. A 1928 description of the drink was: "gin, a spot of lime, and soda“ so let´s just forget about the Vodka. There are quite a few different recepies such as the one created by David A. Embury and published in The Fine Art of Mixing Drinks (3rd Ed., 1958), calling for an 8:2:1 ratio plus garnish. 8:2:1 ratio???
6 cl Monkey 47
1,5 cl Lime Juice
0,7 cl Simple Syrup
Stir all ingredients well in a shaker with ice, then strain into a chilled martini glass. Garnish with a slice of lime.