A Housecarl (sometimes spelled Huscarl or housecarle, originally huskarl) was a professional soldier retained by a Scandanavian king. This term was eventually exported to the Anglo-Saxons during the 11th century who took it to mean warrior who had sworn fealty to a lord. As vassals living in a noble's household. Housecarls were the standing royal fighters of Anglo-Saxon England, comparable to knights elsewhere in Europe.
They were required to have the best quality equipment and if they failed to do so they would be expelled from the Huscarls. They had additional duties acting in their lord's stead in a number of tasks.
Calling one's self a Housecarl is an appropriate thing if one is of a Scandinavian culture where they existed. It represents, as noted above, a professional fighting force.
However this is changed somewhat in the Kingdom of Calontir. In the Kingdom there are two orders which give their members the title 'Huscarl', this being their preferred spelling. These are:
The Order of the Iren-Hirth (for excellence in Heavy Fighting)
The Order of the Boga-Hirth (for excellence in Archery)
Both carry a Grant of Arms in Calontir to represent their high stature. Before creating a persona who is a Housecarl in Calontir, it would be best to check with locals as to the feasibility of this given the stature of the awards.