What is the origin of the word canine related to dogs?

The origin remains mysterious, there is an Old English Word Docga which seems to have been used for a powerful breed of dog. Continental Words such as 'dogue' or 'dogge' are well known. There also Biblical mentions of semi wild dogs that wandered about eating dead bodies and offal in the streets. False apostles have been called dogs by St. Paul. Some servants were also referred to as 'dogs'