noundialect British, South West English
A cave of natural origin in a shoreside cliff.
Late 16th century; earliest use found in John Norden (c1547–1625), cartographer. From Cornish ogo (in place names), gogo, cognate with Old Welsh guocof, Welsh ogof, †gogof, cave, cavern, den.
Orbiting geophysical observatory.
1960s; earliest use found in The Saturday Review.