The Chinese word 脑筋 (nǎojīn) is a compound noun formed through semantic combination, where 脑 (nǎo), meaning "brain", is joined with 筋 (jīn), which originally means "tendon" or "muscle". In traditional Chinese medicine and thought, the "tendons" or "sinews" were associated with strength, connection, and vitality. Thus, when combined, 脑筋 metaphorically extends the concept of the physical brain to represent the "mind", "intellect", or "way of thinking", essentially the "mental tendons" or the faculty of thought, encompassing both innate intelligence and habitual mental patterns.