In Lean Six Sigma, "Lean" refers to a methodology aimed at streamlining processes and maximizing customer value through the elimination of waste. The primary focus of Lean within this context is on efficiency, speed, and continuous improvement. 

Key Aspects of Lean in Lean Six Sigma: 

1. Waste Reduction: Lean targets the elimination of non-value-adding activities in a process, thereby reducing costs and improving efficiency.

2. Customer-Centric: The primary goal is to enhance customer value. This is achieved by focusing on what the customer perceives as value and reshaping processes accordingly.

3. Efficiency and Flow: Lean emphasizes smooth process flow, reducing delays and bottlenecks, thereby speeding up delivery times.

4. Continuous Improvement: It promotes a culture of ongoing, incremental improvements in processes, quality, and customer satisfaction. 
   

Historical Integration with Six Sigma: 

• Origin from Toyota: Lean principles originated from the Toyota Production System, focusing on manufacturing efficiency.

• Merging with Six Sigma: Lean was integrated with Six Sigma, which is focused on reducing variability and improving quality, in the late 20th century.

• Broad Application: Over time, Lean principles have been applied in various sectors beyond manufacturing, evolving into a key component of Lean Six Sigma. 
  

In essence, Lean within Lean Six Sigma brings a focus on process efficiency, waste reduction, and continuous improvement, complementing the Six Sigma emphasis on quality and precision. This integration offers a comprehensive approach for process optimization across various industries.