Ka 家stands for "house" as in "family" and mon 紋 means crest or emblem. The closest equivalent of a mon in the West is a coat of
arms (=monshoo 紋章). The mon tradition has continued from the Heian period to modern days. New mon are even designed today. Most
crest are patrilinear, but in the Kansai region there are also onnamon, matrilinear crests. In addition to family crests, often heralded by
feudal lords (actually, a basis of categorization when searching databases), there are crests for common use, like the kiri (paulownia) leaf
crest. For example my iromuji kimono has a kiri leaf crest in the back. Some of the old family crests have become public property, like the
Maeda crest seems to decorate almost anything in Kanazawa city.
Kimono entusiasts encounter mon on e.g. kimono, haori, and obi. Mon are, however, used to decorate all kinds of objects.
"Montsuki" 紋付 is a word describing an object decorated with a crest. Thus a montsuki kimono is a kimono with a crest /
crests. Before the Meiji period, kamon were mostly used in mens kimono, and it became fashionalble to have mon on womens kimono
only lately.
This might have something to do with the fact that men only have rather formal kimonos, women have a wide range even today. On a kimono,
depending to formality, there can be 1, 3, or 5 crests. The number of crests does not, however, determine the all-over formality of a certain
kimono, since the material, other designs and motifs of the kimono etc. all contribute to the formality level. A crest is meant to dress up a
kimono, just as an obi might do, too. A mon can be dyed or embroidered on komon, iromuji, moofuku, summer moofuku, kurotomesode, and
irotomesode, as well as on haori etc.
A mon of a man is 3 cm or 2,7 (3,8) cm in diameter, and that of a woman is 2 cm (1,9). There are also other kind of mon, like
加賀紋, 祝紋, 月紋, and 花紋. Kaga kamon etc. are also embroidered
around an existing dyed family crest.
On a kimono the top edge of the crest is usually around
Mon come in three versions:
The shape of a mon can vary a lot, but there can be two versions of the same mon: motif in a circle 丸付き, and motife
without surrounding
circle 丸無し紋.
There are sites to aid in finding out what a crest depicts, and what kind of crest a family has.
I know how the name of the family and I want to know what their mon looks like.
On Taimohude's page, type in the name in the search field.
Here is a site with a Otonomiya and either 1) scroll down to find ume in the list or 2) go to the plants section (in the
motif classification menu horisontally at the top) and click on ume in the left pane. In either case I finally arrive to the plum page:
http://www.otomiya.com/kamon/plant/ume.htm.
I get information on the history of the plum design, details about one prestigeous family that has a plum mon (Maeda) and some facts about plum
as a meaningful symbol.
Also okiya have mon. Here is a site with uchiwa fans with okiya mon. We see mon on the obi
of
maiko, decorating the lanterns aorund the hanamachi, even on plates, on napkins and fans etc. Some examples:
先斗町 ぽんとちょう pontocho:
chidori千鳥
and 宮川町 みやがわちょう miyagawacho:
上七軒 かみしちけん kamishichiken:
The capture says this is 岡とめ s 屋形 yakata:

To find matching hiragana and kanji for some of the kamon, here is a site: http://nihonkamonken.hp.infoseek.co.jp/myojikagawaka.htm
You can also search according to location: Noihon Kamon
To find a mon according to its description (e.g. leaf of hemp): Go to Harimaya.
At the index of Harimaya (move mouse over sub headers / links to see romanization at the bottom of your screen)
More kamon sites:
Some search words:
Sometimes kanji are used as crests in addition to kanji being used as other decorations, such as vowen into the fabric etc. The most used kanji:
And just as a thanks for reading this far, wallpapers for your desktop, icons etc. in kamon style.