Genibus = ablative plural of genu ("knee") → "on the knees"
Tunis = likely a proper name or dialectal form (not standard Classical Latin)
Canis = genitive singular of canis ("dog") → "of the dog"
Used to depict abject submission, utter dependency, or grovelling humiliation—someone metaphorically kneeling before a lowly master. Can be derogatory ("cringing") or oddly affectionate ("devoted follower").