I was the other way around. I figured out Ka-Nigits, but didn't understand the insult for years. I just thought it was something funny to say, calling someone's mother a hamster, etc.
If I recall correctly, hamsters are rodents (duh), and rodents are known for their sexual proclivity. So "your mother was a whore". Elderberries were commonly used to make cheap wine, and have a distinctive odor.