Wondering if This German Town Exists?

Hello! I've been doing some research on my maternal great-great-grandparents who immigrated from Germany in approximately the 1880s and were born mid-1860s. Most records (census records, birth records, my grandma's second marriage) only state their birthplace as "Germany". The one exception is their daughter, Alvina's marriage registration that names their birthplace as Slazium or Slaziam, Germany.

I've been playing with the Mayers Gazetteer, and I think it may be a misspelling of Salzdahlum, but I'm not sure since I'm struggling to find any pre-USA records. I'm hoping if I can pin down the area of where they were born, I'll have an easier time finding records (or at least a new starting point!)

Does anyone recognize something similar to Slazium? Or any other ideas of what it could mean? Any help would be appreciated!