Summarize:

Often, breed registries have rules or guidelines for the registered names of horses. Run an online search for any rules that might govern the naming of your type of foal. (For rules on naming a thoroughbred racehorse, see Method Three). Don't run the risk of using their name without permission! Horses' registered names may be derived from those of their sire and dam. You can run an online source for registered horse names. Consider taking the registered name of your horse from the registered names of the horse's parents. In horse breeding, lineage means a lot. Of course, naming your horse after his mom or dad could also have sentimental value. Cabot French Pepper and KVA Hi Time, for example, may lead to a foal named SP Peppertime (in this case, 'Cabot,' 'KVA,' and 'SP' are all prefixes used exclusively by the breeders for their foals). If you don’t particularly care about deriving a name from your foal’s parentage, consider coming up with your own name. Some factors you should consider when naming your horse include appearance, personality, and what you are hoping your horse will do.  Appearance: Does your horse have a unique marking, or a beautiful color worth naming him after? For a horse with a white streak down his forehead (known as a blaze) you might consider naming him Wild Fire or When Lightning Strikes. Personality: Is your horse affectionate, wild, or just a tad mean? A nice horse could be named Honey, a wild one named Midnight Madness, and a mean one named GrumpsMcGee. Occupation: Is your horse going to race? Get featured in parades? Give kids rides? Think about what your horse will do. If you are racing your horse, give her an attention grabbing name like Dream Supreme. If you are a stallion owner, you will be receiving a registration application in the mail when you breed your stallion. If you don’t have one of these applications, you can find the downloadable version online. The information you will need to know to fill out this form includes:  Date foaled Breeding method Embryo transfer date & number Dam's name and/or registration number Current breeding reports Foal description including 5 photos Six foal name choices Other foal information Tax ID or social security number This is when the horse is registered with the breed organization; be careful not to change a horse's registered name if he already has one-- most organizations frown upon this.
Consider his breeding and pedigree. Many barns and breeders use prefixes for horses they breed. Know the traditions observed when naming horses. Come up with an original name. Fill out the registration application. Note when the registered name of a horse is set.