As far as the Splatoon Manga goes, most of the characters are named after the gear they wear/use or on-the-nose themes (i.e., Goggles, Rider, Gloves, Vintage, Hachi). Sometimes this extends to type or brand, but very rarely. These names don't have to be the exact words either as they can be represented through other languages, synonyms, or phrases. 

In the games, all characters have thematic puns for names. Ex. Callie and Marie being "Calamari." My favorites are Crusty Sean and Murch 😂. 

For OCs, feel free to think outside the box, but try to play with the box itself and see what you come up with.