There is no specific text for the History of Competency Based Approaches. However most of us know that it started When Dr.Mcelland published a path breaking paper titled "Testing for Competence Rather than Intelligence" . I have compiled this some time back from various sources both online & offline, hope this would suffice...
Competency-based approaches have developed quite rapidly since their introduction 25 years ago. David McClelland is credited with introducing the idea of "competency" into the human resource literature (Dubois, 1993). In response to a growing dissatisfaction with intelligence testing and the traditional job analytic approaches to personnel selection, McClelland argued that traditional intelligence tests, as well as proxies such as scholastic grades, failed to predict job performance. Instead, McClelland proposed testing for competency.
Competency-based approaches gained popularity and acceptance within the human resources community through the work of McClelland and his associates, particularly Richard Boyatzis, at McBer and Company (which is now part of the Hay Group). Boyatzis is credited with popularizing the term in his book "The Competent Manager (Woodruff, 1991)". Boyatzis suggested that a competency was a combination of a motive, trait, skill, aspect of one's self-image or social role, or a body of relevant knowledge. In other words, a competency is any characteristic of an individual that might be related to successful Performance. Boyatzis' definition of competency left much room for debate over its application to performance.
Klein's (1996) offered one more definition which diverges the most from the others by suggesting that competencies are a collection of observable behaviours, or Behavioral indicators. These Behavioral indicators are grouped according to a central theme, which then becomes the competency. Klein suggests that the behaviours underlie the competency; this is contrary to other definitions which suggest that competencies underlie behaviours.
Woodruff raised the issue of distinguishing between competence and competency and proposed that competence is a performance criterion while competencies are the behaviours driving the competence. More recently, Rowe raised the same issue and discusses competence in terms of a skill and a standard of performance and defines competency as the behaviour needed to achieve competence. This is similar to Klein's argument that competencies are not psychological constructs but thematic groups of demonstrated observable behaviours that discriminate between superior and average performance. These behaviours require no inference, assumptions, or interpretation.
Zemke's comments at that time on the definition of competency remain valid today:
"Competency, competencies, competency models, and competency-based training are Humpty Dumpty words meaning only what the definer wants them to mean. The problem comes not from malice, stupidity or marketing avarice, but instead from some basic procedural and philosophical differences among those racing to define and develop the concept and to set the model for the way the rest of us will use competencies in our day-today efforts." ( Zemke, 1982, p.28)