The Collaborative International Dictionary of English v.0.48:

Tetter \Tet"ter\, n. [OE. teter, AS. teter, tetr; akin to G.
   zitter, zittermal, OHG. zittaroch, Skr. dadru, dadruka, a
   sort of skin disease. [root]63, 240.] (Med.)
   A vesicular disease of the skin; herpes. See Herpes.
   [1913 Webster]

   Honeycomb tetter (Med.), favus.

   Moist tetter (Med.), eczema.

   Scaly tetter (Med.), psoriasis.

   Tetter berry (Bot.), the white bryony.
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The Collaborative International Dictionary of English v.0.48:

Tetter \Tet"ter\, v. t. [imp. & p. p. Tettered; p. pr. & vb.
   n. Tettering.]
   To affect with tetter. --Shak.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Eczema \Ec"ze*ma\, n. [NL., fr. Gr. 'e`kzema; "ek out + zei^n to
   boil.] (Med.)
   An inflammatory disease of the skin, characterized by the
   presence of redness and itching, an eruption of small
   vesicles, and the discharge of a watery exudation, which
   often dries up, leaving the skin covered with crusts; --
   called also tetter, milk crust, and salt rheum.
   [1913 Webster]