The Collaborative International Dictionary of English v.0.48:

Stringency \Strin"gen*cy\ (str[i^]n"jen*s[y^]), n.
   The quality or state of being stringent.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

67 Moby Thesaurus words for "stringency":
   Spartanism, acerbity, acidity, acridity, acrimony, astringency,
   austerity, authoritarianism, bite, bitterness, causticity,
   chinchiness, chintziness, demandingness, discipline, edge,
   exactingness, exiguity, fewness, fierceness, grimness, grip,
   hardness, harshness, inclemency, infrequency, keenness, meagerness,
   meticulousness, miserliness, mordacity, mordancy, niggardliness,
   paucity, poignancy, point, rarity, regimentation, restrictedness,
   rigid discipline, rigor, roughness, ruggedness, scantiness,
   scarcity, scrimpiness, severity, sharpness, skimpiness, smallness,
   sparseness, sparsity, sternness, sting, stinginess, strictness,
   stridency, tartness, teeth, thinness, tightness, toughness,
   trenchancy, ungentleness, vehemence, violence, virulence