eczema

Eczema is a learned borrowing from Latin eczema, itself from Ancient Greek ἔκζεμᾰ (ékzemă, 'cutaneous eruption'). That Greek word comes from ἐκζέω (ekzéō, 'to boil out, break out') plus the nominal suffix -μᾰ.

The word kept its original sense fairly closely: a 'breaking out' or eruption on the skin, passed from Greek into Latin and then into learned English medical vocabulary.

The verb ekzéō, meaning 'to boil out' or 'break out,' is the direct ancestor tucked inside the word — the facts don't point to any other English cognate.