The name Challah:
Bread in Hebrew is called Lechem while the separated dough is called Challah. It is customary to call the Shabbos bread Challah in order to serve as a reminder to women to separate Challah from the dough.[1] In previous times, it was common in many communities to refer to the Shabbos bread as “Barchas.” The reason for this is because these Challahs serve as a channel of blessing during the Shabbos meal.[2]
_____________________________________________
[1] Ashel Avraham [Butchach] 260
[2] Piskeiy Teshuvos 243 footnote 88