Othea was a mountain goddess taken by Annam, the primal giant, as his wife. With Annam, her children were the progenitors of the various "true" giant species: hill giants, stone giants, frost giants, fire giants, cloud giants, storm giants, voadkyn, ettins, and titans. She had several extramarital affairs, resulting in illegitimate children. With Vaprak she mothered the race of ogres and with Ulutiu she birthed the races of firbolgs, verbeegs, fomorians, and voadkyn (although this last is disputed). Cyclopes and cyclopskin are also thought to be the result of one of Othea's affairs. She was poisoned by her mortal son (with Annam) Lanaxis and died, her last child with Annam trapped in the womb caves of the mountain that was her material manifestation.
At least, so it is said on the world of Toril. Other worlds have other myths.
Source: Giantcraft, Faiths & Pantheons