I am six months pregnant. My husband and I conceived our baby eight days after my
father passed away and I would love to name the baby after him.
I understand that we must use the first letter of his name to
honor him. Can you please tell me why this is and what it means?
I don't really know the tradition. Also, does it have to be his
first name or can we use his full name for a middle name? I want
to do the right thing but I also want to understand why. Thank
you VERY much!

Shalom, Mazal Tov, and may your
birth be healthy and at a good time. The custom to use the name
of family members is very old (see Midrash Bereishit Raba 37,
37 which says that in the days when people had prophecy they named
their children after events, but "now"- this book was
written over 1200 years ago- we name after our ancestors). It
is a widespread, and very proper practice, as well as, apparently,
having spiritual benefits for the deceased. (In the Sephardic
world they name after living grandparents, but Ashkenazic Jews
name after only dead relatives).
The name a person has expresses-
and reveals, qualities of their soul. This being so, one should
only name the child after someone who had qualities that one would
like the child to emulate. I'm sure your father possessed many
such qualities that you would wish to see in your future child.
For the same reason, many people are careful not to name after
someone who died a tragic or painful death, or who died at a very
young age. In such a case they change the name slightly (Yeshiyahu
to Yeshiyah) or add a different second name (commonly Chaim, which
means life).
You can use your father's complete
name, or one of his names- though there are communities that are
very particular to name exactly after the name of the deceased
(e.g. if his name was Moshe Mendel, they call the child Moshe
Mendel, not more not less). It is also fine to use the name as
a first or second name, or even to combine names (the child is
named Shlomo Jacob- "Shlomo" after the grandfather,
"Jacob" after the great uncle) but in such a case it
is a good custom to use both names in addressing the child (not
just special occasion such as being called up to the Torah).
I did not find a source for using
the initial of someone's name, but many people use similar sounding
names, especially if the name is inappropriate. So a relative
named Harry may become a Chaim in Israel, or a Zelda (a nice Yiddish
name that unfortunately is the name of the personnel carrier vehicle
in the Israeli army) will become a Zahava, etc. All this is perfectly
fine, as the main idea is to take the name of a departed relative
and pass on the name- and hopefully the good traits of the deceased
person- to the next generation.
You can even change the sex of
the name- Baruch to Bracha- Dina to Dan etc.- when necessary.
Some people are very interested/worried
about the spiritual ramification of all types of combinations
of names. If your run you lives based on the Kabbalah, then it
would be good to speak to a knowledgable Kabbalistic rabbi about
the name. But, if this is not your inclination, you should choose
the name yourselves which you like and you feel best honors your
late father. It is said that the parents get near prophecy in
determining the names of their children.
I will add that apart from the
name influencing the character traits of the child, that there
is a spiritual tradition that if a child is born to a family within
a year of the passing of a family member, it brings great benefit
to the departed soul, and it is very fitting to name the child
after them.
May your father's memory be for
a blessing- Rabbi D. Sperling