"ropy lava," 1859, from Hawaiian.
A type of lava having a smooth, swirled surface. It is highly fluid and spreads out in shiny sheets. Compare aa.
Our Living Language : The islands that make up Hawaii were born and bred from volcanoes that rose up over thousands of years from the sea floor. Volcanoes are such an important part of the Hawaiian landscape and environment that the people who originally settled Hawaii, the Polynesians, worshiped a special volcano goddess, Pele. Not surprisingly, two words have entered English from Hawaiian that are used by scientists in naming different kinds of lava flows. One, pahoehoe, refers to lava with a smooth, shiny, or swirled surface and comes from the Hawaiian verb hoe, "to paddle" (since paddles make swirls in the water). The other, aa, refers to lava having a rough surface and comes from the Hawaiian word meaning "to burn."