I don't think explanations of the popularity of car and cdr need to be any more complicated than that they were the first and hence using them was consistent -

I don't think explanations of the popularity of car and cdr need to be any more complicated than that they were the first and hence using them was consistent - also two 3 letter keywords are better than any alternatives I've ever seen proposed. They could happily be called left and right without any inconsistency with implementation.