lava (n.)
1750, from Italian (Neapolitan or Calabrian dialect) lava "torrent, stream," traditionally from Latin lavare "to wash" (see lave). Originally applied in Italian to flash flood rivulets after downpours, then to streams of molten rock from Vesuvius. Alternative etymology is from Latin labes "a fall," from labi "to fall." Lava lamp is attested from 1965, also lava light (reg. U.S., 1968, as Lava Lite).