Meaning

noun rock that in its molten form (as magma) issues from volcanos; lava is what magma is called when it reaches the surface

originFrom Italian, from Neapolitan and Sicilian lava (“lava; downpour overflowing the streets”), likely from Latin lābēs (“a fall; a collapse; subsidence”); compare lābīna (“landslide”). A supposed relation with lavare (“to wash”) is now widely discredited, nor is there probably any relation with Arabic لابة (lāba, “black volcanic rock”). Alternatively, the Romance words are connected with Provençal…

Etymology from Wiktionary, CC BY-SA 3.0