The Term Manchu appeared as early as 1613 and came into use after 1628. Not until 1635 did 'Manchu' replace 'Jurchen' etc., the traditional names of the people in question. The origin and meaning of the term Manchu have puzzled scholars since the first half of the 18th century and there has evolved about a dozen interpretations. The least known and possibly the most likely is a Korean, from 1711, where 'Man' is explained as 'ten thousand Jurchen warriors' and 'chou' by implying 'continuing prosperity'. (Pei Huang, The Origin of the Manchus, p. 273).
In 1582 the Jurchen leader Nurhaci embarked on an inter-tribal feud that escalated into a campaign to unify the Jurchen tribes. By 1616 he proclaim himself Khan of 'Great Jin' in reference to the previous Jurchen dynasty. Two years later he openly renounced the suzerianty of Ming's overlordship in order to complete the unification of those Jurchen tribes still allied to Ming Dynasty. After a series of successful battles he relocated his capital from Hetu Ala to successively bigger captured Ming cities in the province of Liaodong, first Liaoyang in 1621 and again in 1625 to Shenyang or Mukden. Nurhaci's unbroken series of military successes came to an end in January 1626 when he was dealt his first major military defeat by general Yuan Chonghuan while laying siege to the Ming city of Liaoning. He died a few months later.
Modern scholarship on the rise of the Manchu emphasizes the contributions of Chinese collaborators to the Manchu cause. The Manchu offered rewards and high positions to these Chinese, who not only brought military skills and technical knowledge with them but also encouraged the adoption of Chinese institutional models. From Chinese and Korean artisans the Manchu learned iron-smelting technology and acquired the advanced European artillery of the Ming. They created a replica of the Ming central government apparatus in their new capital, Mukden (present-day Shenyang), established in 1625. Whereas Nurhachi had initially based his claim to legitimacy on the tribal model, proclaiming himself khan in 1607, he later adopted the Chinese political language of the Tianming ("Mandate of Heaven") as his reign title and in 1616 proclaimed the Hou (Later) Jin dynasty. Abahai continued to manipulate the political symbols of both worlds by acquiring the great seal of the Mongol khan in 1635, and thus the succession to the Yuan dynasty, and by taking on a Chinese dynastic name, Qing, for his own dynasty the following year. (In Encyclopædia Britannica. Retrieved April 28, 2007)
As a term, the Manchus were largely a political entity whose formation corresponded with the unification of the Jurchern tribes by Nurhaci (1559-1626) after 1583. The term Manchu first appeared during Nurhaci's reign and came to use shortly after the succession of Nurhaci's eight son Hong Taiji to the throne. In 1635, it was officially coined as the name of Hong-taiji's subjects, who by now consisted of Mongol, Chinese and Corean components in addition to various Jurchen groups. Hong-taiji's adoption and enforcement of the new name gave a unity to aristcrats, commoners and slaves from all Jurchen, Mongol, Chinese and Korean peoples, inhabitants and tribes that was now ruled as one people and, consolidate his claim for superiority. On this basis Hong-taiji in 1636 proclaimed himself the first Emperor of the Qing Dynasty. (Pei Huang, The Origin of the Manchus, p. 282).
Some sources suggested that the name "Qing" was chosen in reaction to that of the Ming Dynasty which consists of the Chinese characters for sun and moon, which are associated with the fire element. The character Qing is composed of the water radical and the character for blue-green, which are both associated with the water element. At the same time this name change would have demonstrated a full understanding of Han Chinese values heavily influenced by a Neo-Confucian education system.