'arsinic' originates from New Latin/Modern Latin, specifically formed from the word 'arsenic' (from Latin 'arsenicum' / Medieval Latin) with the adjective-forming suffix '-ic', where 'arsen-' referred to the element 'arsenic' (from Greek 'arsenikon').

'arsinic' changed from the Medieval/Latin root 'arsenicum' plus the suffix '-ic' (used to form adjectives), and eventually became the modern English adjective 'arsinic'.

Initially it meant 'of or pertaining to arsenic' and over time it has retained this core meaning as an adjective describing substances or properties involving arsenic.