OED:

rare. 

[ad. Ger. tarnkappe.]

A magic cap, securing the invisibility of the wearer.

1856 R. A. VAUGHAN Mystics (1860) I. 3 Rings of Gyges, coats of darkness, tarn-caps, and other means of invisibility. 1863 C. M. YONGE Chr. Names II. 312 Siegfried, by means of his tarn cap, invisibly vanquished the Valkyr.

I’ve just sent in an antedate to the OED, from 1825:

the tarn-cap, or invisible hat

Tarn-cap also appears in Adolf Hitler’s Mein Kampf.

they rapidly pulled the tarn-cap of lies over their ears

Nifty.  Do they sell those at Harrod’s?

Eliza, is this tarn any relation to Poe’s “dank tarn of Auber, iin the ghoul-haunted woodland of Weir”?

OED on tarn:

[ME. terne, a. ON. *tarnu, tjorn, tjörn; = Swed. dial. tjärn, tärn, Norw. tjörn, Da. tjern.]

A small mountain lake, having no significant tributaries. (Originally local northern English, now generally used by geologists and geographers.)

[1256 Assize Roll 979 m. 10d (Westmorland), Agnes..appellat..Edelinam filiam Ricardi de Blaterne [= Blea-tarn] quod ipsa dederat ei potum mortiferum bibere.]

It doesn’t seem so.  I think Poe’s referring to the lake. Picture below of Blea Tarn in the English Lake District:

link

edited links

Larry Sommers - 25 April 2007 12:53 PM

Eliza, is this tarn any relation to Poe’s “dank tarn of Auber, iin the ghoul-haunted woodland of Weir”?

It is a shame that so many know Poe for the madness of The Raven and The Cask of Amontillado, and know nothing of the sadness of Ulalume or the The Bells.

I’ve come across it as the “tarnhelm”.  Didn’t it also enable the wearer to understand the speech of birds, or was that another magic hat?

I believe that it did, at least in Wagner’s version of the legends, and also gives the power of changing one’s appearance, although my knowledge of this is mostly derived from Tom Holt’s Expecting Someone Taller (a very funny book, if you like light fantasy).

Edit: Whoops!  According to various synopses of the Ring cycle on the Web, it was the blood of the dragon Fafnir that gave Siegfried the ability to understand birds’ speech, not the tarnhelm.