text: The term ‘acid sulfate soils’ (ASS) was coined by the Working Party on Nomenclature and Methods for the first International Symposium on Acid Sulfate Soils (1972, Wageningen) to mean soils that contain, or have the potential to produce, sulfuric acid in quantities that cause significant and long-lasting changes in key soil properties. This term was gradually adopted by the international scientific community for the sake of international consistency and cooperation. Prior to this, different regions used colloquial terms such as: 
  * argilla vitriolacea (Latin, ‘clay with sulfuric acid’ – coined by Carl Linnaeus);
  * Kattekleigronden or Katte Klei (Dutch, ‘cat clay’);
  * Gifterde (German, ‘cursed / poisoned earth’); and 
  * Maibolt (an Austro-Germanic spirit or creature that, when angered, would curse the soil to spoil crops).
  The term ‘acid sulfate soil’ is useful for general discussion, but fails to capture nuances required for technical classification of soils. Additional terms such as ‘potential acid sulfate soil’ (PASS), ‘active acid sulfate soil’ (AASS) and ‘post-active acid sulfate soil’ (PAASS) helped researchers distinguish between the following: 
  * PASS: non-acidic soils that did not contain substantial quantities of sulfuric acid, but contained the necessary materials to produce it under certain conditions; 
  * AASS: soils that were acidic due to the presence of sulfuric acid; and 
  * PAASS: soils that were once active acid sulfate soils, but have since weathered or ‘ripened’ to the point they were similar to ‘normal’ sub-aerial soil in terms of their chemical and physical properties (e.g., pH and drainage). 
  As a single soil profile may contain PASS, AASS, and PAASS at different depths, the term ‘material’ was added as a modifier (i.e., PASS-material, AASS-material, and PAASS-material) to allow for more nuanced descriptions of complex soils. However, these terms are still somewhat awkward and unsuitable for technical classification. Additionally, acid sulfate soils and the variations thereof imply that acid sulfate soils are an altogether different type or class of soil, rather than a feature soils may exhibit under certain conditions. Consequently, there has been a gradual movement away from these terms in favour of more standardised, operationally-defined definitions.