The Collaborative International Dictionary of English v.0.48:

Fuller \Full"er\, n. [AS. fullere, fr. L. fullo. See Full, v.
   t.]
   One whose occupation is to full cloth.
   [1913 Webster]

   Fuller's earth, a variety of clay, used in scouring and
      cleansing cloth, to imbibe grease.

   Fuller's herb (Bot.), the soapwort (Saponaria
      officinalis), formerly used to remove stains from cloth.


   Fuller's thistle or Fuller's weed (Bot.), the teasel
      (Dipsacus fullonum) whose burs are used by fullers in
      dressing cloth. See Teasel.
      [1913 Webster]