I’m nostly documentning a couple of weird but not completely abstruse ones here.
Iverson and Whitney
Arthur Whitney is i think the creator of the odd ill-explained k and b languages which make impressive claims about performance and unimpressive claims about community, support and longevity. I think they are in the APL lineage as created by Kenneth E. Iverson.
The hoary old classic of esoteric languages, about which I am no authority. However, check out this homomorphic encrypt brainfuck machine.