I'm not related to YDSEs or ELLINGAN/ELLINGSANs but I found a wonderful letter a few years ago at an antique sale. I bought it because it contained a lot of genealogical info and I thought it would have a better chance of me finding a family member who wanted it, than it would sitting in a box of photos at a travelling antique shop.
Here is the info contained in the letter. It is written by Anna YDSE of Lillesan, Verdalen on Jan 26, 1913. I won't type out the whole thing, but here are the main points, translated. It is written in Norwegian and addressed to Mrs. Mary ELLINGAN of Webster, Sask.
Anna is the daughter of Oluf YDSE, who is Mary's uncle. Anna came to Verdalen in 1906. They bought Lillesan (I'm assuming it is a farm) which is close to a place called Rinbret. Anna and her family lived in "Jarlen" prior to Lillesan, and Mary's father visited them there.
Anna has a sister named Martine, who at the time of the letter was married and living in Salberg. Her brother Johan worked on the railroad at Davre / Dovre.
Anna has a son, three years old whose father is in Canada. Anna hopes to live there soon, like Mary. Apparently Mary visited Norway but did not get to meet Anna or her family because the Ydses were in Sweden.
I get the impression that Anna is using her maiden name, YDSE. This idea may be further supported by the existence of a family in the 1900, Stjoerdal, Nord-Trondelag census that fits the bill:
Oluf Ydse b. 1849 in Verdalen & wife, Mali
Martine Ydse b. 1880 in Hegre
Anna Ydse b. 1883 in Meraker
Johan Ydse b. 1887 in Sweden
Since it seems Anna's father was Mary's father's brother, then Mary's maiden name would have been YDSE as well.
Ellingan or Ellingsan would have been Mary's married name.
At the time this letter was written Mary had small children.