In Spanish, it means chain; in French (if you add an “s” to the end) it means lock. Either way, it seems that somebody secured the resolution they wanted. Now we know why the action was discontinued.
In text (the notice is on the KnitPicks website, too):
Special Note: In August, our Sierra yarn line will be renamed to Cadena – the exact same fiber content, construction and weight, just a brand new name, and we’ll be adding new colors!