'arginase' originates from the word 'arginine' (the amino acid) plus the enzyme-forming suffix '-ase' (coined in Modern scientific nomenclature for enzymes).

'arginase' was formed in modern scientific English in the late 19th century by attaching the suffix '-ase' to 'arginine,' producing the name for the enzyme that acts on arginine.

Initially it meant an enzyme acting on arginine, and this primary meaning has been retained in modern usage.