The story
First attested in 1668, in the singular on July 3rd and in the plural on December 19th; Latin: correus (“partaker in guilt”, “co-defendant”) + dēbendī (“of that which is to be owed”, the genitive singular of the neuter substantive of the future passive participle of dēbeō, “I owe”) = “one jointly liable for something owed”.
Etymology from Wiktionary, CC BY-SA 4.0.