caar cddddr

(cadr list), (caddr list), ... -- every c{a,d}+r name from two to four levels deep.

Each composite accessor applies a sequence of car/cdr operations read right to left: cadr is (car (cdr x)), caddr is (car (cdr (cdr x))), cddr is (cdr (cdr x)), and so on through all 2-, 3-, and 4-level combinations up to cddddr. Like car/cdr, applying one to nil along the way yields nil instead of erroring.