The answer to the title question: a confusing lot. “Onym” is a word syllable stemming from an ancient Greek root, meaning “name,” which form parts of many English words, particularly those that describe unusual characteristics of some English words.

When writing and speaking, the “onym” syllable usually identifies words that share either the same spelling or sound while encompassing a different meaning. Confusing? Just wait until I explain. We all know and use synonyms (similar meaning) and antonyms (opposite meaning), but may not be familiar with other “onym” words. Consider a few:

Homonym: words that impart multiple meanings while sharing either the same sound or spelling; like, bare (naked)/bear (animal), fair (exhibition)/fair (just). We cannot stop here without first mentioning other homonym subcategories; namely:
— homophone, which describe words that sound alike with different spelling and meaning like aisle/ isle; here/hear;
— homographs, which describe words that spell alike, with different meaning, as bear (uphold)/bear (animal)
— heteronym which classifies words that share the same spelling, but have different sounds and meanings, like close (shut) and close (near)

Oronym: phrases that sound the same, but differ in spelling and meaning, like: Gray day or Grade A; stuffy nose or stuff he knows.

Capitonym: words that spell or sound the same, but differ in that one word carries an initial letter capital; like, Polish (nationality) and polish (shine); Turkey (nation) and turkey (bird).

Paronym: words that are “similar”, not necessarily identical, but contain a significantly different spelling, like accept/except, addition/edition

Acronym: an abbreviation using the initial letters of each word in a phrase; like Scuba (Self Contained Underwater Breathing Apparatus) or Nato (North American Treaty Organization.)

Contronym: a word having two meanings that contradict one another, like sanction, which may mean to approve or to boycott; moot, which may mean a debatable point or a point not worth debating.

Conclusion: An onym by any other name may qualify as a pseudonym.