Mawson, C.O.S., ed. (1870–1938). Roget’s International Thesaurus. 1922.

Class III. Words Relating to Matter
Section II. Inorganic Matter
1. Solid Matter

324. Softness.

   NOUN:SOFTNESS, pliableness &c. adj.; flexibility; pliancy, pliability; sequacity [obs. in this sense], malleability, ductility, ductibility, tractability, tractility, extensibility, extendibility; plasticity; inelasticity, flaccidity, laxity, flabbiness, flocculence; mollescence, mollification; softening &c. v.
  [COMPARISONS] clay, alumina, argil; wax, putty, butter, dough, pudding; cushion, pillow, feather bed, down, eider down, padding, wadding.
   VERB:SOFTEN; render soft &c. adj.; mollify, mellow, milden, tender [rare], gentle [rare], dulcify; relax, temper; mash, knead, massage, squash [colloq.].
  BEND, yield, relent, relax, give.
   ADJECTIVE:SOFT, tender, supple; pliant, pliable; flexible, flexile; lithe, lithesome; lissom, limber, plastic; ductile, ductible [rare], tractile, tractable; malleable, extensile, extensible, lax, sequacious [obs. in this sense], inelastic; aluminous; remollient [obs.], mollient, mollescent, mollitious, mollified.
  yielding &c. v.; flabby,| limp, flimsy.
  flaccid, flocculent, downy; spongy, œdematous or edematous, medullary, doughy, clayey, argillaceous, mellow.
  soft as-butter, – down, – silk, – putty, – a feather bed; yielding as wax; tender as a chicken.
   QUOTATION:Smoothing the raven down Of darkness till it smil’d.—Milton