Bertha Marie Jordan
Not much detail is known about Bertha Marie Jordan, the mother of Paul Erdmann, other than that she was born in Germany (or rather the then German Empire), and she had 5 children, 2 or 3 of which survived to adulthood. Researching women pre-1900s is particularly difficult, because not much documentation was made related to them, other than that which pertains to their husband or father.
From Paul Erdmann's birth certificate, I ascertained that she is likely a child born out of wedlock, as she shares a maiden name with her mother (Merz), but was adopted by her father-in-law, Mr. Friedrich Jordan. Her mother actually shares most of her name as well, identified in the document as Marie Jordan. This practice of naming children mostly the same given name as their parents was very common for the time period.
We also know that her religion was Protestant, while her husbands was Catholic, as per the birth certificate. This is interesting, as the differences between the two religions was particularly contentious in Germany, due to it being the birthplace of Lutheranism and a major spark in the fire that became the Protestant Reformation. Catholicism was (and is) particularly prominent in the former Bavarian Kingdom and present State of Bavaria located in southern Germany along the Alps. This is the most Catholic state in Germany with more than 50% of those surveyed identifying as Roman Catholic in 2016.
Tragically, she and her husband, Bernhard Erdmann both passed away in December of 1910, mere months after their child Paul moved to America, thus unable to spend their final moments with him. Given the proximity of their deaths, this would likely be due to a serious illness which infected them both. Again, this was incredibly common for the time.