You know what’s nifty? This word.
OK, OK, but seriously: a word like nifty is a nifty thing. Toss it in and you get just the right feeling – it’s a nifty little language trick. It doesn’t have any obvious relation to other words, and it doesn’t get used all that often, but it just fits neatly in its niche.
Its niche, for its users, is largely defined by the words it’s most often seen with: according to the Corpus of Contemporary American English, these include little, trick, features, pretty (as in pretty nifty little trick), gadgets, stuff… You notice the tone and usage context of these words: not exactly formal; more endearing, fun, like things you use to charm a person (e.g., yourself) into buying a thing. Its synonyms (thanks, Merriam-Webster) include boffo, choice, crackerjack, groovy, jim-dandy, keen, neat, primo, righteous, swell, top-shelf, and a number of more formal words up to and including supernal (which might be a bit strong and self-regarding, to be honest).
But where does it come from? Hmm, that we don’t know. Its first published use – in 1865 – declares that it comes from Latin magnificat, but that is, as the Oxford English Dictionary puts it, unlikely. More likely it has influence from the sounds of other words: natty, thrifty, spiffy (and perhaps the nif in magnificent); it has a nice lift to it, and though it may have some sounds of iffy and shifty, that neat nose of an n seems to set it up more nicely and endearingly. The /ɪ/ vowel is high, but not as high as /i/, so it’s small and sweet but not saccharine. The /ft/ is a soft touch, of course, and the y suffix adds a bit more diminutive potential. So it’s niftily put together: a clever little lexical doodad that serves the turn, not just denotation but connotation and a certain sense of fondness.
The ensemble of it may seem almost more to match style than substance: not so much intelligent as fashionable. Fair enough; although it has meant ‘ingenious’ for a long time, its first sense was ‘stylish, attractive’, a sense it has retained in some quarters up to the present. So you can call someone’s bowtie nifty and mean that it is pleasing to the eye or that it is stain-repellent and doubles as a beer opener. Either way, it’s smart… at least in the eyes of certain beholders.