We're talking about typed FP so only SML in your list really counts. So let's see: functors, polymorphism, higher-kinded types (does SML have those?), Hindley-Milner type inference, etc. Then for Haskell (the main topic of the linked article), bring in a bunch of unfamiliar algebra such as the notorious monoid on the category of endofunctors. It is actually worth understanding that. I liked this article (prerequisite: some exposure to Haskell):
There's not really an official definition of FP. There are some proposed ones that involve types and some that don't involve them. Mainly though, this is a thread about the linked article, which is about the tribulations that the author had learning Haskell. Most of those tribulations were with the type system and I think that matches most people's experience. You can't transplant it to Lisp.
I like your sense of humor.
Appeal to Wikipedia Fallacy: https://en.wikipedia.org/wiki/Functional_programming
LISP certainly shows up in the discussion. It's even called the first functional programming language!