Great Houses are more prevalent in the mortal lands, as succession holds slightly more stake when house heads can die of natural causes, along with the regular ones. Traditionally, houses are named after the first name of the member of the house that put it on the map.
For instance, in the Human lands of Midgard, Camaen Weaver, who invented a sheep-mounted spinning wheel that revolutionized textile production, did not found House Camaen, his great grandson did, Cam (Camaenion) Weaver of House Camaen.
Most of the first names throughout the Realm (especially in the early days) are based upon the proto language whispered in the cosmos before the beginning, but in the modern day, many other naming traditions have taken root throughout the Realm.
The base of a name are appended through generations within families. Neutral names may have no added ending, or end in -or or -phen.
Masculine names end in --on or -ron; brothers end in -chon, -chanar or -dor; sons end in -ion or -rion; young men end in -dir or -ndir; bridegrooms end in -daer, and married men end in -ben.
Feminine names end in -el, -eth, il, -ril or -ien; sisters end in -thel or -nith; daughters end in -iel, ien, rien or -riel; young women end in -des, -ndes, -hel or -neth; maidens end in -wen -gwen, -dis or -ndis, and married women end in -bes.
Surnames in the Realm vary somewhat by region and time period, but are commonly related to a familial trade (Fisher), trait (Greatheart), power (Flametower) or affinity (Nightlore). Mortals usually and even immortals often have simpler surnames (Earthmaker, Oakroot), while immortals, particularly the ones created in the early days of the Realm, would frequently choose surnames that served as titles (Duvainil of the Dusk).
Surnames were sometimes passed on through familial lines in some cases (mortals more than most, Humans in particular), but Realm-wide will just as often be a variant upon one or both parental names, or even a completely unique name.
There aren't any hard rules, is what we're saying, unless perhaps you're a noble.