Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
plethora (n.)
has long meant an unfortunate, undesirable overabundance of something: She’s had a plethora of telephone calls today. But semantic change is causing it to appear in Edited English meaning simply “a lot of something (but not too much) not necessarily bad at all, but neither good nor bad, or in some instances, downright good.” If enough Standard users keep on using plethora in these senses, the meaning of the word will change. Meantime, make context support your pejorative use of it.
