euphemistically yours

in today's nyt, there's an article about a van gogh painting that's going to auction. but it's not really about that because in mere column inches the story veers from the painting into the far juicier world of love and its sweatier consigliere to discuss various artists whom the original collector had known (not in the biblical sense, gutterhead, but in the friendship/patron sense) and specifically of one woman who bore un enfant exactly nine months after she "modeled" for both degas and renoir. not at the same time, alas.

would love to know the euphemism used for a threesome.