Attempt of a bit more serious answer. Based on my experience of reading Lisp manuals since approx. fiveteen years the most often used words for Lisp's dashes are "hyphen", "hyphenation", and "hyphenated".
After digging some old Lisp manuals at:
it appears to me as if until the late 1970s long symbol names in Lisp were just simply written as LONGSYMBOLNAMES. The two main predecessor Lisps before the Common Lisp unification were Interlisp and MacLisp. While Interlisp barely uses hypens in symbol names, in MacLisp many long symbol names were written with hyphens. This means that if there is any explanation for the use of hyphens in long Lisp symbol names then it must be found either in some old MacLisp docs or in the pre-CLtL1 discussions between the MacLisp and Interlisp developers.
The most obvious reasons why Lisp uses hyphens and not underscores or CamelCase are:
- A hyphen needs one key, while an underscore can only be typed using the SHIFT key (= minimum two keys).
- Lisp uses prefix syntax, where "X minus 1" ist typed as (- X 1) and not as x-1. Using infix syntax is the reason why languages like C are forced to forbid hyphens inside variable and function names and use the more awkward underscore instead.
- Using CamelCase makes not much sense in Lisp, because in many Lisp languages symbol names are internally converted to uppercase. Common Lisp can be told to work with case-sensitive symbol names, but this does not work in all Lisp languages.