a mount point for a pendrive
 

Where does KDE get a mount point name for an inserted pendrive from? There is fat32 and no label.
It mounts it as "/run/media/<username>/openSUSE-13.1-DVD-x86_640091/". There was opensuse on this stick before, but I deleted all partitions and formatted the drive.

IFAIK, the name is coming from udisks/udisks2. Just take a look at https://wiki.archlinux.org/index.php/udisks for more info.

Welcome to LQ!

I think the mountpoint is named after the disk's label.
Relabel the disk / partition to change the mount point.

GParted shows that there is no label.
mlabel: Volume has no label
udisksctl shows IdLabel with old label, before formatting. Is udev caching uuids and labels connections?

[QUOTE Is udev caching uuids and labels connections?][/QUOTE]
It's possible, but I would find this annoying.
You could try assigning a new UUID and see what happens (let us know either way please)

Setting a new label has solved the problem. I hadn't done it before, because I tried to find the reasons. The partition type is 83 (Linux), but the filesystem is vfat, maybe there's something left from the previous content.

As I understand it UDEV deals with the mouting of devices by UUID and if you ever use a device not labelled at all this is apparent. So, I would then assume that if a label is present a given device will be mounted under a mount point with that name and I see no reason for the mount point for a device to change unless the label changes to another string -- i.e. if it's blank then the old one would be used.
The above is just guesswork but based upon messing with a few USB drives over a fairly long period of time.

Good, and thanks for the follow-up.

"Partition type" and filesystems mounted on them have caused me some head-scratching in the past. But when it "just worked", I moved on (I'm lazy, I know).

Had you not fixed the problem, I'd have asked you to look at the output of cat /etc/blkid.tab, but it seems your Q is A'd already.

Best wishes.

"No such file or directory" (Arch)

I set a new label "test" - the mount point changed to "test"
I deleted the label... the mount point is "openSUSE-13.1-DVD-x86_640091" again. So I went back to square one.

dd if=/dev/zero of=/dev/sdX count=1 bs=1M
it will make udev forget about openSUSE.

P.S.
Be sure you running dd on correct device. And it should be entire device, not a partition (e.g. /dev/sdd, not /dev/sdd1)

Ok, but where does the system keep uuid <> mountpoint relationships? It's not Windows with it's messy registry.

AFAIK, system doesn't keep UUID to mountpoint relationship.
What does blkid show? Has your stick opensuse label still? If so, dd it.

Is there anyone provide information about AFAIK ??

All utilities showed there was no label.

dd did the trick. Next I created a new partition, a new filesystem, and there is no "opensuse..." anymore, even without any label.
Thank you.