Lava
mid 18th century: from Italian (Neapolitan dialect), denoting the lava stream from Vesuvius, but originally denoting a stream caused by sudden rain, from lavare ‘to wash’, from Latin.
wiktionary
From Italian lava(“lava”), originally, in Naples, a torrent of rain overflowing the streets, either from lavare(“to wash”) (see etymology for the English verb lave) or from labi(“to fall”).
etymonline
lava (n.)
"molten rock issuing from a volcano," 1750, from Italian (Neapolitan or Calabrian dialect) lava "torrent, stream," traditionally said to be from Latin lavare "to wash" (from PIE root *leue- "to wash"). 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, slip" (see lapse (n.)). As an adjective, lavatic (1805), laval (1883). Lava lamp is attested from 1965, also lava light (reg. U.S., 1968, as Lava Lite).
