'subcutaneous' originates from Latin, specifically the Medieval Latin word 'subcutaneus', where 'sub-' meant 'under' and Latin 'cutis' meant 'skin'.

'subcutaneous' changed from Medieval Latin 'subcutaneus' into English (scientific/medical use) as 'subcutaneous' in the 18th–19th centuries; the adverbial form 'subcutaneously' was formed by adding the adverbial suffix '-ly' to the adjective.

Initially it meant 'under the skin' in a literal anatomical sense; this core meaning has been retained, now used both descriptively and in medical contexts (e.g., injections given beneath the skin).