Grotchec could be Grotchev (which I believe is Bulgarian).
Let me run these risky speculations :-) ==>
The OP's "Grotchec" could be as well a name of a village, or a castle Grodziec (German: Gräditz or Grodzietz, Czech: Hradec, Old Polish: Grodziecz, Grodez, Grodecz, Grodzecz, Grodzeycz). It all comes from the old word "grodza, grodze, grodz", which means an embankment, or a palisade. From there also comes "grodzisko" - a stronghold, and also "gród" - a stronghold, a settlement, a town.
There are eight villages "Grodziec" in Poland, en.wikipedia.org/wiki/Grodziec - all across Poland, three hills and one town district of that name. There is also one castle in Lower Silesia and one small castle (a manor) - in Silesia. This is the one that might be of interest here:
A village and a small castle Grodziec (Cz. Hradec, Ger: Grodzietz), gmina (municipality) Jasienica, powiat (district, county) Bielsko, Silesian Voivodship (Province).
It was also a part of Principality of Bielsko - first as a lower rank principality (Fürstentum), then as a Duchy (Herzogtum Bielitz), created by Austrian Queen Maria Theresa in 1752 and 1754, correspondingly. The principality was owned by six Sułkowskis from 1752 to 1848. Their residence was the Castle in Bielsko (now Bielsko-Biała), a.k.a. Castle of Dukes of Cieszyn, a.k.a. Sułkowskis' Castle. Today it hosts Bielsko-Biała Museum, en.wikipedia.org/wiki/Bielsko-Bia%C5%82a_Museum_and_Castle.
Grodziec is located about 18 km west of Bielsko-Biała, a capital of Bielsko district.
The Grodziec castle is currently privately owned, and undergoes renovation. In XII c. there was a wooden stronghold ("grodzisko") there, owned by a knight named Świętosz, from the village Świętoszówka nearby. In XIV c. a masonry castle stood there, owned by Pełka. In XVI c. the land around Grodziec was given by Casimir II, a Duke of Cieszyn, to a knight of Radwan coat of arms. It is unclear whether his family name Grodecki came from the Grodziec, or the other way around.
In 1542-1580 a new castle was built by Maciej Grodecki, Castellan of Cieszyn, and his son Henryk. The Grodeckis were a known clan: three Grodeckis became starosts of Cieszyn and several others became clerics, including one archbishop and one famous cartographer, In 1650, after the death of the last of the Grodecki clan, the castle was owned by Marklowski family (Wieniawa coat of Arms), then by Jan Dama from Biedrzydowice, Karol Jerzy Sobek, Henryk Ferdinand Larisch, and then again by Marklowskis clan.
In the centuries that followed its ownership was changing many times. In 1927 it was owned by dr. Ernest Habicht, a friend of Józef Piłsudski, and an avid collector of ancient objects and books. During the WWII, after a German field hospital was established there, the collections of dr. Habicht have been devastated. After the war the castle hosted the Experimental Institute of Animal Husbandry from Puławy.