Sources differ as to the etymology of Quraysh, with one theory holding that it was the diminutive form of qirsh (shark). The 9th-century genealogist Hisham ibn al-Kalbi asserted that there was no eponymous founder of Quraysh; rather, the name stemmed from taqarrush, an Arabic word meaning "a coming together" or "association". The nisba or surname of the Quraysh is Qurashī, though in the early centuries of Islam, most Qurayshi tribesmen were denoted by their specific clan instead of the tribe. Later, particularly after the 13th century, claimants of Qurayshi descent used the Qurashī surname.
The Quraysh's progenitor was Fihr ibn Malik, whose full genealogy, according to traditional Arab sources, was the following: Fihr ibn Mālik ibn al-Naḍr ibn Kināna ibn Khuzayma ibn Mudrika ibn Ilyās ibn Muḍar ibn Nizār ibn Maʿadd ibn ʿAdnān. Thus, Fihr belonged to the Kinana tribe and his descent is traced to Adnan, the semi-legendary father of the "northern Arabs". According to the traditional sources, Fihr led the warriors of Kinana and Khuzayma in defense of the Ka'aba, at the time a major pagan sanctuary in Mecca, against tribes from Yemen; however, the sanctuary and the privileges associated with it continued to be in the hands of the Yemeni Khuza'a tribe. The Quraysh gained their name when Qusayy ibn Kilab, a sixth-generation descendant of Fihr ibn Malik, gathered together his kinsmen and took control of the Ka'aba.[note 1] Prior to this, Fihr's offspring lived in scattered, nomadic groups among their Kinana relatives.
All medieval Muslim sources agree that Qusayy unified Fihr's descendants, and established the Quraysh as the dominant power in Mecca. After conquering Mecca, Qusayy assigned quarters to different Qurayshi clans. Those settled around the Ka'aba were known Quraysh al-Biṭāḥ, and included all of the descendants of Ka'b ibn Lu'ayy and others. The clans settled in the outskirts of the sanctuary were known as Quraysh al-Ẓawāhīr. According to historian Ibn Ishaq, Qusayy's younger son, 'Abd Manaf, had grown prominent during his father's lifetime and was chosen by Qusayy to be his successor as the guardian of the Ka'aba. He also gave other responsibilities related to the Ka'aba to his other sons 'Abd al-'Uzza and 'Abd, while ensuring that all decisions by the Quraysh had to be made in the presence of his eldest son 'Abd al-Dar; the latter was also designated ceremonial privileges such as keeper of the Qurayshi war banner and supervisor of water and provisions to the pilgrims visiting the Ka'aba.
According to historian F. E. Peters, Ibn Ishaq's account reveals that Mecca in the time of Qusayy and his immediate offspring was not yet a commercial center; rather, the city's economy was based on pilgrimage to the Ka'aba, and "what pass for municipal offices have to do only with military operations and with control of the shrine". During that time, the tribesmen of Quraysh were not traders; instead, they were entrusted with religious services, from which they significantly profited. They also profited from taxes collected from incoming pilgrims. Though Qusayy appeared to be the strongman of Quraysh, he was not officially a king of the tribe, but one of many leading sheikhs (tribal chieftains).
According to historian Gerald R. Hawting, if the traditional sources are to be believed, Qusayy's children, "must have lived in the second half of the fifth century". However, historian W. Montgomery Watt asserts that Qusayy himself likely died in the second half of the 6th century. The issue of succession between Qusayy's natural successor, 'Abd al-Dar, and his chosen successor, 'Abd Manaf, led to the division of Quraysh into two factions; those who backed the 'Abd al-Dar clan, including the clans of Banu Sahm, Banu 'Adi, Banu Makhzum and Banu Jumah, became known as al-Aḥlāf (the Confederates), while those who backed the 'Abd Manaf clan, including the Banu Taym, Banu Asad, Banu Zuhra and Banu al-Harith ibn Fihr, were known as al-Muṭayyabūn (the Perfumed).
Toward the end of the 6th century, the Fijar War broke out between the Quraysh and the Kinana on one side and various Qaysi tribes on the other, including the Hawazin, Banu Thaqif, Banu 'Amir and Banu Sulaym. The war broke out when a Kinani tribesman killed an 'Amiri tribesman escorting a Lakhmid caravan to the Hejaz. The attack took place during the holy season when fighting was typically forbidden. The Kinani tribesman's patron was Harb ibn Umayya, a Qurayshi chief. This patron and other chiefs were ambushed by the Hawazin at Nakhla, but were able to escape. In the battles that occurred in the following two years, the Qays were victorious, but in the fourth year, the tide turned in favor of the Quraysh and Kinana. After a few more clashes, peace was reestablished. According to Watt, the actual aim in the Fijar War was control of the trade routes of Najd. Despite particularly tough resistance by the Quraysh's main trade rivals, the Thaqif of Ta'if, and the Banu Nasr clan of Hawazin, the Quraysh ultimately held sway over western Arabian trade. The Quraysh gained control over Ta'if's trade, and many Qurayshi individuals purchased estates in Ta'if, where the climate was cooler.
The sanctuary village of Mecca had become a major Arabian trade hub. According to Watt, by 600 CE, the leaders of Quraysh "were prosperous merchants who had obtained something like a monopoly of the trade between the Indian Ocean and East Africa on the one hand and the Mediterranean on the other". Furthermore, the Quraysh commissioned trade caravans to Yemen in the winter and caravans to Gaza, Bosra, Damascus and al-Arish in the summer. The Quraysh established networks with merchants in these Syrian cities. They also formed political or economic alliances with many of the Bedouin (nomadic Arab) tribes in the northern and central Arabian deserts to ensure the safety of their trade caravans. The Quraysh invested their revenues in building their trading ventures, and shared profits with tribal allies to translate financial fortune into significant political power in the Hejaz, i.e. western Arabia. In the words of Fred Donner: