At first, I thought "misnomer" was an English word adapted from Latin (still learning, as you can see). Yet, it seems it does not exist in Latin. According to Wikipedia:
From Anglo-Norman mesnomer, noun use of Anglo-Norman and Old French verb mesnomer (“to name incorrectly”), from mes- (“mis-”) + nomer (“to name”) (from Latin nōmināre).
So, given this assertion, would not the Latin equivalent be "mesnomer"? However, Wiktionary does not yield an entry for such word. Neither does S&L dictionary. Why is such not a word? Am I incorrectly understanding the above quoted text?