Russian pet names
Searched: Googled "Russian pet names," "Russian affectionate names," and "Russian affectionate names +Judith"
Situation: I'm looking for an affectionate nickname an elder Russian man might use on his American mentee, a woman named Judith. Both have an extended lifespan (she is nearly a century old, and he's better than double that), so while she is significantly younger than he and is studying under him at a renowned research institution, she wouldn't merit the sillier type of pet name used for, say, a child.
Does anyone have any suggestions or guidance? Thanks so much in advance!