I have practiced onomancy but I thought it was called one's name number in numerology. Thankfully A Word A Day provides clarification in definition, pronumciation and uses.
MEANING: noun: Divination by the letters of a name.
ETYMOLOGY: From Greek onoma- (name) + -mancy (divination). Earliest recorded use: 1603.
NOTES: Some parents name their children after careful consideration of onomancy to assure the best possible future for them. Some people alter the spelling of their names or adopt a new name in an effort to bring good fortune. Science fiction writer Isaac Asimov wrote a short story, "Spell My Name with an S", with this theme. The story was inspired by his frustration in having to ask people to spell his name (pronounced AZ-uh-mof) correctly.
USAGE: "Kaplan and Bernays taught me all sorts of unexpected things about my name. They inspired me to try my hand at alphanumeric onomancy, in which the letters of a name are assigned numerical value, then added up to reveal occult facts about its owner."
Adam Goodheart; Naming Names: An Appellation Spring; The Washington Post; Feb 3, 1997.
Explore "onomancy" in the Visual Thesaurus.
If you are interested in checking compatibility using onomancy, try this Destiny Onomancy site.