If you have a “kitchen with all the bells and whistles,” you have all the accessories and appliances that most people can think of — but even without them, it’s still a kitchen. “Bells and whistles” can be found in practically any field. Here’s an unusual application from 2010: “One would think that most chief financial officers, tax executives and business owners take full advantage of all the bells and whistles provided in the United States tax code.”
Basically, “bells and whistles” are whatever isn’t basic. Additional features that might be useful or attractive, but not necessary. The phrase probably comes from something that had actual bells and real whistles: steam trains. At least in the US, steam trains all had bells, ringing whenever they chugged along in a populated area in order to warn people off the tracks. And they also all had whistles, which they blew as a long-distance warning or announcement that they were approaching an intersection, coming into the station, or leaving in just a moment.
Although bells and whistles could be found on all US steam locomotives, in England the bells are said to have been fairly rare. This wasn’t because the English were generally more attentive and didn’t need extra warnings to keep out of the way — it was sort of the opposite. After a certain point, all English railways were fenced off, the idea being that it was next to impossible to accidentally wander onto the tracks if you couldn’t reach them. And in any case, each train still had a perfectly good whistle.
The phrase “bells and whistles” can be found in the 1800s, but in those days it was simply used in relation to trains: “You look up at an angle of sixty degrees and see sweeping along the edge of a precipice, two-thirds up the rocky height, a train of red-and-yellow railway-cars, drawn by two wood-burning engines, the sound of whose bells and whistles seems like the small diversions of very little children, so diminished are they by the distance.”
It’s not clear when people began to realize that (1) maybe having both bells AND whistles was a bit redundant, and (2) they could use the phrase to describe anything that wasn’t strictly necessary. It was used at least as early as the 1960s (that citation about the kitchen is from 1963), and since then it’s grown in popularity — maybe because practically everything nowadays comes with even more bells and whistles.