Trivial name
In organic chemistry, trivial name is a non-systematic name (often established by historical precedence) that is permitted within the IUPAC nomenclature system for ease of reference to molecules whose names would otherwise be too cumbersome for everyday use.
For example, the fairly common dicarboxylic acid "tartaric acid" (found in wine) has a systematic name of 2,3-dihydroxybutandioic acid, quite a sour mouthful.