'low-intensity' originates from Modern English compounding of 'low' and 'intensity'. 'low' ultimately comes from Old English 'hlāw' where it meant 'not high; close to the ground', and 'intensity' comes from Latin 'intensitas' via French 'intensité', where the Latin root 'intens-' (related to 'intendere' / 'tendere') conveyed the idea of 'stretching' and, by extension, 'force' or 'strength'.

'intensity' entered English via French 'intensité' in the early 17th century from Latin 'intensitas'. 'low' developed from Old English 'hlāw' into modern 'low'. The compound 'low-intensity' arose in Modern English (notably in the 20th century) in technical and descriptive contexts such as medicine, exercise, and military terminology.

Initially the phrase simply combined the senses of 'low' + 'intensity' ('not intense'), but over time it acquired specialized technical uses (for example, 'low-intensity conflict' and 'low-intensity exercise') to label particular categories rather than only serve as a general descriptor.