The name of the
cons function is not unreasonable: it is an
abbreviation of the word “construct”. The origins of the names for
cdr, on the other hand, are esoteric:
is an acronym from the phrase “Contents of the Address part of the
cdr (pronounced “could-er”) is an acronym
from the phrase “Contents of the Decrement part of the Register”.
These phrases refer to the IBM 704 computer on which the original Lisp
The IBM 704 is a footnote in history, but these names are now beloved traditions of Lisp.