This language is not very good, but I made it in an afternoon.

It is unnamed and will hence be referred to as 'SL' for stack language because I cannot come up with anything else.
SL is my first attempt at making a concatenative language. Its not great. Also all stacks in SL are from right to left (to allow for left to right function composition). I have since determined this to be a 'bad move' but will talk more about that later in this.

Code in SL looks like this:

fibb 10

`(

= "fibb" lambda "x" (

    ` 

    < x 2 

    (x) 

    (+ fibb - x 1 fibb - x 2)

))

This code evaluates to the following stack:
[55 !]
I tried to use the 'nil is identity' trick I use in loon , but that doesn't work in this case. It does at least have less parens than loon though.