'thyroid-suppressing' originates from Modern English as a compound of 'thyroid' and the present participle 'suppressing'. 'thyroid' ultimately comes from New Latin 'thyreoideus' (from Greek 'thyreoeidēs'), where 'thyre-' (from Greek 'thyreos') meant 'shield' and '-oeidēs' meant 'resembling'. 'suppressing' comes via English from Latin 'suppressus' (perfect passive participle of 'supprimere'), where the prefix 'sub-/sup-' meant 'under' and 'primere/primere' (from 'premere') meant 'to press'.

'thyroid' changed from Greek 'thyreoeidēs' to New Latin 'thyreoideus' and later entered English as 'thyroid'; 'suppress' comes from Latin 'supprimere' → Old/Middle French/Latin-influenced forms → Middle English 'suppressen' and then modern English 'suppress', with the present participle 'suppressing' forming compounds like 'thyroid-suppressing' in Modern English.

Initially, 'thyroid' referred to a 'shield-like' anatomical structure (the thyroid cartilage); over time it came to name the gland itself. 'Suppress' originally meant 'to press down' and evolved to mean 'to inhibit or restrain'. Combined, the compound now specifically denotes 'causing inhibition of thyroid function'.