Everyday things that no one would recognize today
A recurrent Science Fiction theme is a man from the past coming to the present, where he’s totally baffled by our modern technology and its products. We tend to forget that this would work both ways…

Look at this glass object: any idea what it is?
It is, in fact, a cup; that is, a glass vessel used for the ancient alternative medicine practice of Cupping. These would be placed over or around a flame to heat the air inside, then applied to the patient’s back where the partial vacuum created by the cooling air would suck at the skin to improve blood flow (and if you nicked the skin, you could get some bloodletting action to boot).
In years past, this was a well known part of the arsenal of medicine in many countries, and anyone would recognize it… in fact, in my native Hebrew this practice survives in the old expression “beneficial like cups for a dead man”, used to denote utter uselessness.
But the point I want to make is, today this is definitely not well known; apart from some adherents of Chinese medicine, no one would recognize this once-common device. There are many other such objects to be found if you only look around in attics, bottom drawers and antique stores: items whose function no young person alive today would even be able to guess, though their grandparents still might.
Here are a few more:

A rocker blotter, which uses blotting paper to soak up excess ink from a written page. Standard office gear before ballpoint pens. I got this one for my Bar Mitzvah, though it was already dated even then.

Candle snuffer and wick trimmer. You could also blow on the candle, but these useful implements did a cleaner job.

Gramophone needles, from the days of “His Master’s Voice”… these wore out so fast you bought them by the box.

An inkwell, in this instance a hermetic traveler’s version.

A ceramic light switch. These were fixed above the wall surface, not inside it. So were the electric wires, held on ceramic insulators like the one shown here. Those were the early days of “electrification”, when electric power was retrofitted to existing homes.

A magic lantern slide, one of the earliest entertainment media. In the absence of TV, it must’ve been a big deal for the children! And if you happen to be in the Hague, seek out the museum of the magic lantern – you’ll be amazed what our ancestors could do with this technology.

An Ice pick, a ubiquitous tool when refrigerators were “Iceboxes” — literally. You’d buy big heavy blocks of ice, then smash and chip them with one of these. Also useful as a cinematic murder weapon…

A Blue Amberol phonograph cylinder, from the Edison company (that’s him on the box). The original form of voice recording media, which was ultimately ousted by the flat Gramophone disc records.
And lastly, already on the endangered list…

Yes, a Typewriter. I was enjoying the Office equipment museum of Tom Russo in Wilmington, with its room after room of typewriters spanning a century only recently gone, and was amazed to learn that visiting groups of schoolchildren do express bewilderment at the function of this device!
Sic transit gloria mundi…