Onomastics is the study of proper names, their origins, and their usage. Antonyms for onomastics would therefore be words that describe the opposite of this, such as "unfamiliarity with names," "lack of interest in names," or "ignorance of names." Some possible antonyms could include "anonymity," "namelessness," "non-identification," or "anonymousness." Alternatively, words like "amnesia," "forgetfulness," "desuetude," or "disuse" could indicate an absence of knowledge or awareness of proper names. Ultimately, whatever term is chosen, it should convey the opposite of the intellectual curiosity and attention to detail that onomastics represents.