The Commodore Business Machines logo, which strongly

resembles a poultry part. Rendered in ASCII as "C=". With

the arguable exception of the Amiga, Commodore's computers

are notoriously crocky little bitty boxes (see also

PETSCII). Thus, this usage may owe something to Philip

K. Dick's novel "Do Androids Dream of Electric Sheep?" (the

basis for the movie "Blade Runner"; the novel is now sold

under that title), in which a "chickenhead" is a mutant with

below-average intelligence.