'anergic' originates from Greek, specifically the word 'anergos,' where 'an-' meant 'without' and 'ergon' meant 'work.'

'anergos' was adopted into scientific English as 'anergy' in the late 19th century, and the adjective form 'anergic' was later derived from it.

Initially, it meant 'without energy or work,' but over time it evolved into its current medical meaning of 'lacking an immune response.'