chock » chalk(ed)
The title of Mark Liberman’s 2004 Language Log piece gives a whole pile of variants: “Chock, choke, chuck, check, chalk, jock, shock, chog: An ancient plantation of ache-corns”. “Choke-full” is the original (with “chuck-full” and “chock-full” as early variants); “chock-full” is now the dominant variant. “Chock” doesn’t make much sense, so it’s no surprise that people have attempted to re-shape it. The connection to chalk is obscure (Brians: “Chalk has nothing to do with it”), but at least “chalk” is a reasonably common actual word (and homophonous with “chock” for some speakers).
“Chalk full” has been reported at least five times in the ecdb comments pages.
[added 4 September 2011, from an ADS-L posting by Larry Horn:
One point that’s not mentioned in the write-ups at the Eggcorn Database is the possibility of reinterpretation due to the Northern Cities vowel shift, which notoriously affects vowels in words like “chock”, “chuck”, and “chalk”. While homophony is possible, as Arnold observes in the [entry above], but there’s also the clash … between the “before” and “after” dialects, those without and those with the Northern Cities shift, so that someone (non-shifted) saying “chalk” [COk] would be heard (by a shifter) as saying “chuck”. A very brief summary of such shifts is available here, where “stock”, “stuck”, and “stalk” are exemplified. ([See the] wiki entry here.)]