Comment by jlokier
The names CAR and CDR weren't invented for Lisp or FLPL. They came from assembly language mnemonics on the IBM 704, where the first Lisp interpreter was implemented.
The original Lisp CAR and CDR operations used the machine-level instructions with those names on the IBM 704.
Cons cells were stored in single words of the 36-bit memory and 36/38-bit registers, and the CAR and CDR operations accessed the "address" and "decrement" 15-bit parts of a word, respectively.
That's the legend, but they're actually no such instruction mnemonics.
The Address and Decrement terms and the fields of the 36-bit word they denote do come from the architecture.
There are instructions like LXA and LXD -- load index from address, load index from decrement.