magma

The word 'magma' was borrowed directly from Latin, which itself took it from the Greek 'μάγμα' (magma), meaning 'a thick unguent' or 'kneaded dough'. The Greek term derives from the verb 'μάσσειν' (massein), meaning 'to knead'. This etymological journey from the concrete act of kneading a pliable substance to the geological term for molten rock is a classic example of semantic shift. The logic lies in the shared property of viscosity and malleability; just as dough is a soft, mixable mass, so is the hot, fluid rock within the earth. The modern scientific usage, established in the 19th century, retains this core sense of a thick, flowing, formative material.

The entire word is a simplex loanword from Greek. It is not productively segmented using its modern English spelling into meaningful sub-parts like 'mag' and 'ma'.