1 þerna
u, f. a tern or sea-swallow, sterna hirundo, Grág. ii. 347, Edda (Gl.); spá-þerna, Hkr. i. (in a verse), and in mod. usage: in the local name þern-ey, near Reykjavík.
2 þerna
II. a servant, [Dan. tærne; quite a different word, akin to þirr]:—a maid-servant, Stj. 138, 172, 616, and so in mod. usage.