As a total aside, the names `car` and `cdr` for "head" and "tail" are honestly some of the most baffling historical relics in all of computing.
The concept is to make things easier for people who are familiar with the language. Making things harder for that group is always counterproductive, because they are the only people who can do any useful work.
Also, Back In The Old Days memory was very expensive and precious so short identifiers were important. Often labels were tightly constrained, for example being limited to six upper-case characters so they would fit in a single word.
More characters on the other hand prevents many potential types of mistakes, such as meaning one statement of target and actually entering another.
CAR = Contents of the Address part of Register
CDR = Contents of the Decrement part of Register
I also love how the register names don’t even have ANY mnemonic relation to what the contents mean in Lisp. Address and Decrement? Totally arbitrary. It’s like having a high-level language where function parameters are always names rsi, rdi, and so on. Because obviously "destination index" means "first argument"!
Something I tell junior developers: There is one way to correctly spell out a word in full, but many different ways of abbreviating it. Don't make me guess or memorise which one you chose, completely arbitrarily.
UNIX and languages "born from it" are especially prone to a ludicrous level of abbreviation because of its start in the earliest days of computing when serious machines had mere kilobytes of memory, and so every byte was precious. Compounding that were the use of teletypewriters, which did not generally allow edits and were glacially slow. Tab complete was impossible.
This has become so ingrained in the early generation of computing science pioneers that they passed on these behaviours almost like religious doctrine, like dogma or rituals that must be preserved. Perhaps it was mostly subconsciously done, but I have seen programmers in the 90s and early 2000s still instructing others to do these things, to shave bits and bytes off identifiers to 'save space'.
Computers used to have very little memory and processing power, and screens had very low pixel density so line width was not that big. Then you have to deal with the baggage 50 years later.
Modern Lisps have the luxury so they use head/tail or first/rest.
Look at the words in the Swadesh list[0]. They are all short.