A Java applet is basically a plugin module that you need to install.

Javascript, on the other hand, is integrated in the web browser, so you don't have anything to install. And it really is full integrated, so you can have:
onclick='return confirm("ok to delete?")'
inlined directly in the html code.

This above is obviously not an application - not even a small application. It is just a code fragment.

The specific thing with an applet is that it is run in a container or as a plugin.

Javascript doesn't run in a container and isn't a plugin. It is just a way of integrating code fragments within a web page.

You know what? You really should care. Because you most definitely cares if someone assembles C, compiles assembler etc.

The word Applet really is a very specific term. Just as microcontroller is a very specific term that is incorrect to use about a Pentium processor.

You are quite unprofessional if you say "arbitrary definition a bunch of code geeks try to impose", when the electronics industry is a similar bunch of electronics geeks who try to impose definitions like zener diode, tunnel diode, avalance, trisil, diac, ...

And you really are right. The word Applet is taken. Have been for over 30 years now.

Either start randomly use electronics terms for what they are not, to back your claim that terms aren't important. Or stop complaining.