No, I don't assume that. But I think that that's irrelevant. People didn't know "def" means function in Python or Scala either, but they learn it on the first day and don't have a readability problem with it.
Very basic keywords like "fn" are not the things that make a language unreadable, nor is calling the keyword "fn" instead of "function". Those are memorized in a day or so and you're done with it.
It's other things that make languages unreadable (too many sigils, overloaded operators or keywords in different contexts (C++, Perl), single letter operators (e.g. APL), too low level, too much verbosity, etc.
In any case, whether a person that first encounter a language immediately recognizes what a keyword means is not what makes the language readable. It's how readable it is to its programmers, after they know the language and have written code in it that matters. Familiar != readable.
>Everybody and their grandma can read Pascal and Ada, but abbreviated keywords and magical symbol require foreknowledge.
And almost everybody and their grandma dislike their syntax (especially Ada's), and would prefer something less verbose.
>And the more abbreviated, the more you will have to continuously look up things in the reference manual until they get cemented.
It's after such basics "get cemented" that readability comes into play, not before. If someone has to look after 2-3 days with the language what "fn" means or how to declare a function (and similarly, "def" in Python/Scala, etc), they have some serious memory issues.
(Btw, Rust, Clojure, and others also use "fn").
>Not sure what you mean here - discriminant unions? classes?
Yes, aka variant, aka tagged union, aka sum type...