The ancient Greeks used the most common ancient Gk term for dog, κύων, sometimes as an insult. There's a relatively recent book on this matter (2014) by Cristiana Franco, Shameless: The Canine and the Feminine in Ancient Greece (transl from Italian; Univ. of CA Press; original Italian 2003). She argues that ancient Greeks did not generally view dogs with hostility, although they disliked certain dog behaviors. To that end, see the proverb in 2 Peter 2:22-- κύων ἐπιστρέψας ἐπὶ τὸ ἴδιον ἐξέραμα, "A dog returns to its own vomit." But ancient Greeks and ancient Jews valued dogs also as guards, hunting companions, protectors of sheep, and traveling companions. I defer to modern Gk speakers regarding σκύλα for the b-word.
Odysseus calls the suitors dogs before he kills them (22:35)-- Ω κύνες! There's also a strong positive dog motif in the Odyssey, as just prior to the suitors scene Odysseus is recognized by his faithful old dog who has been mistreated by the same suitors. The description is perhaps the most beautiful dog scene in all of literature. Also, Odysseus' rage at the suitors' dishonor of himself, his house, his son, his wife, and his dog gives rise to an incredible metaphor in which his rage is described in canine terms (20.13-16 his heart was barking in him / as a mother dog stands over her puppies when a stranger comes and barks and rages to fight / so Odysseus' heart barked...") So the ancient Gk term for dog was used as an insult even as dogs were beloved and/or respected for multiple reasons. That is, ancient Greeks had complex relationship with dogs. They were aware that many dogs were wild, flea-ridden, and mangy, while they also valued dogs for their noble qualities.
There are several comments about this. It seems even native Greeks don't agree just be sure both are acceptable.
Have a look here...it may help.