The person I'm tracking (not the hypothetical match; this is family lore) came from Odessa, perhaps was a tailor. And being a tailor was a common occupation for Jews in Odessa. Jews settled in Odessa after the Russians took it over, and that community was attempting to assimilate in Russian society, giving up its Germanic roots in the process. They were German enough to try out a rabbi from Germany -- but committed enough to assimilation for him not to take.
The hypothetical match immigrated in 1890 which is early enough that ellisisland.org can't help me out. And that, too, fits well: the early 1890s in Odessa were a time when Jewish rights were being curtailed: they were about a third of the population of the city and had been participating in municipal politics -- until they were banned from doing so. Hardly a promising sign.
If this candidate turns out to be the right one, my step-father-in-law had a wise grandfather: he got out before things turned really ugly.