Like other people have said, the -son ending is exclusively masculine -- I would understand appending it to 'Matt' if you were having a son, but with a daughter? It makes no sense. Also, think of the incredible difficulty your daughter will have throughout her life: her name will be constantly mispronounced and misspelled. As someone whose own name is constantly mispronounced and misspelled, I can tell you that it's a huge annoyance and, now that my career is gaining traction, a potential professional liability.
I appreciate that this name has a great deal of significance for you, but it just isn't practical to use. I would suggest using it in the middle or finding an alternative. Bear in mind that you may very well have a son, in which case you'll probably want to use Matthew as his first or middle name.
As for alternatives, how about...
Amata or Amatia
There is a great deal of pressure when someone wants to name a child in this manner. It is really hard to say no. I think that it's a bit one sided to say you not only want to name somebody to honor somebody else, but that there is only one acceptable way to do so. I would not want my child being named in this way. I would want some options, and I think the important thing is not what I think about the name, but what you think about the name and whether your husband is being reasonable about HOW he wants to honor his brother. Either way I am sorry he lost his brother and wish you all the best.
Originally Posted by raechel
Have you considered using Mattie as the full name, instead of Mattison? I agree with you that the rule of -son endings equaling boy isn't so stringent today but it does still sound really masculine to me. I knew a Mattie who was named that because her parents didn't like any of the full names (Matilda, etc). Since it's the signficance you're after, does it work? Out of curiosity, what are your other girls named?
I'm going to disagree with the mispronunciation and misspelling claims being made.
Just looking at it, I think the pronunciation of Mattison is very straight forward.
As for spelling, if someone said Mattison the only error that may happen is that someone may omit the second 't'... which is something fairly common with most people who have spelling with a double letter.
Growing up with someone (female) who had the surname Mattison none of these things were ever an issue.
You found a cute nickname and you yourself appreciate the significance of it... I'd go for it.
How about Matisse, for another Mat name?