Reference:
http://blog.scrumstudy.com/how-to-identify-risk/

Takeuchi and Nonaka proposed that product development should not be like a sequential relay race, but rather should be analogous to the game of rugby where the team works together, passing the ball back and forth as they move as a unit down the field. The rugby concept of a "Scrum" (where a group of players form together to restart the game) was introduced in this article to describe the authors' proposal that product development should involve "moving the Scrum downfield".
Reference: http://blog.scrumstudy.com/the-story-behind-origin-of-scrum/

Quality is required not only in products, but also in processes. Quality assurance refers to the evaluation of processes and standards that govern quality management in a project to ensure that they continue to be relevant. Quality assurance activities are carried out as part of the work. In fact, quality assurance is a significant factor of the definition of Done. The deliverable isn't complete if appropriate quality assurance has not been conducted. Often, quality assurance is demonstrated during the Sprint Review Meeting.