mermaid are not real. mermaids are half women and half fish.
I think Merman is Tritón in Spanish. Even for the Lizard Newt it is Tritón in Spanish. Mermaid it is Sirena in Spanish. Not sure about Merfolk in Spanish.
There is no suffix in mermaid, but there is a prefix. The prefix is "mer", the original word is "maid".
Nereids
Yes, Just the Spanish version.
The French word for mermaid is sirene. The Latin origin for this word is serene, and it appears in the Romance Languages and also in the Phillippines for the word mermaid.Another French word for mermaid is la luxure, which means double-tailed, referring to double-tailed mermaids.There are two famous mermaid stories from France, one is called Melusina and the other is Ondine.
hooriyya حورية
2
maheli~heli
Maid is the most obvious word you can make from mermaid. You can also make the words mire, mare, made, and aid.
Irish Gaelic: maighdean mara
The spanish word for guitar is Guitarra. This English word came directly from the Spanish word, but it is not a Spanish word any more than the Spanish word is an Arabic word. "qutar" or a Greek word Chirara.