- He (or possibly his son) was the first to actually bear the "Esthland" Arms; his branch is traced from his great-grandfather Gotthard-Wilhelm von Rosenberg.
Why the new arms? It has to do with this branch's abandonment of estates they held; they are in fact a matter of some disgrace. This is from Vol. 1 of The von Rosenberg Family of Texas (8):
"The lineage was indigenous to Kurland but not to Esthland. The barons living in Kurland at Garossen Estate from 1500 AD on bought more and more property in Esthland; after about 1741 other estates appear on the charts (from the Froelich book) especially near Ragnit and Memel, such as "Wintzheim," "Holwigshof," "Laugsch," and the more familiar "Raddeilen" and "Eckitten." Friederich Wilhelm von Rosenberg was the first owner of the Raddeilen near Memel, but he also acquired other estates. The first owner of Eckitten was Wilhelm's son Sigismund Gustave, who acquired it in 1749.
"In 1786, for some cause related to the Krottingen War, the family emigrated from the Garossen Estate in Esthland. This ‘departure by seal' caused them to be known ‘in disgrace' for leaving an old home in a native land. For fighting in the Krottingen War and other reasons the family, or at least Otto (b. 1772), was granted more charges to be used on the coat of arms; but it had to include the ‘lion rampant regardant'--looking backward--because the family had affronted the old arms by leaving it. By permission of the College of Arms the name was changed from Kurland to Esthland, a new grant was given, but the old one retained in case any descendant desired to use it. Otto inherited Eckitten in 1793 and chose to live there instead of at Garossen because the lands were better and the surroundings and educational opportunities better for children.
"Peter Carl [the immigrant], the grandson of Sigismund Gustav, also chose to live at Eckitten, although Garossen was not sold and was occupied by Peter Carl's brother Gustav and his wife Ida. Gustave and Ida reared, at Garossen, two orphaned sisters of Eleanore von Rosenberg-Froelich, the sisters of LIbussa Froelich who was broght to America when she as 10 years old."