I spotted the name Masson in a news article recently, and my first instinct was to say MASS-on (short a).
Masson was meant to be a form of Mason, but I couldn’t force myself to pronounce it that way. Why? Because vowels before double consonants are typically short.
For instance, compare the words on the left with the words on the right:
See what I mean? When Masson’s parents doubled the s, they actually changed the pronunciation of their son’s name.
Same with Suzzanna, which I saw in a phone book a couple of weeks ago. Suzzanna is supposed to be a form of Suzanna, but doubling the z ends up shortening the u. That first syllable now rhymes with buzz instead of with bruise.
So if you’re thinking about doubling a consonant, or throwing in any other superfluous letters, check first to make sure the alteration won’t affect the name’s pronunciation.