भगीरथात् from Bhagiratha, ककुत्स्थ: Kakutstha, येन by whom, काकुत्स्थाः as Kakutsthas, विश्रुताः are celebrated, ककुत्स्थस्य च to Kakutstha, रघुः Raghu, पुत्रः son, अभूत् was born, येन by whom, राघवाः Raghavas

To Bhagiratha was born Kakutstha, by whom your race is wellknown. A son Raghu was born to Kakutstha and hence all of you are known as Raghavas.