You must avoid at all costs including personal information like your exact date of birth or your house number in your online dating username.
Dubious characters are always looking to collate such personal information and then misusing the identity of hapless victims.
Different dating services call them handles, nicknames or just usernames, but they all mean the same thing.
Your username is the identity you project to the world of online dating sites and the secret to a great username is to not make a bad one!
It is best to avoid overtly sexual connotations or racy language in your username and online profile as it may attract the wrong kind of people, oh unless you are registering with a specialist introduction site or only looking for sexual liaisons.