For this Duncan Fergus there are 2 different names on Yasni.
In the ranking of the most common first names Duncan Fergus is on position 4589.
Male first name (English): Duncan, brown (haired) warrior; Old Irish (Word format); donn = brown; chadh = the warriors
Male first name (Irish, English): Fergus, a man of strength, Old Irish (Word format); fear = the man, gus = the force strength, in Irish legend is a warrior-prince Fearghas