"Wouldn't the Wave be more aptly called 'aikuchi' due to it's tsuka-less design?" - KA

The reply came...

"The word “tan” in “tan-to” is an adjective meaning “short” (with a connotation of “very short”); “to” is a noun meaning “katana” (the same kanji as in Nihon-to, but “to” is an “on-yomi” pronunciation). Therefore, “tanto” is a type of edged weapon with a very short blade of usually less than one “shaku” (i.e., 30.3cm) from machi to kissaki. A tanto may or may not have a tsuba when it is properly mounted, but such is irrelevant because as long as the blade is very short (less than one “shaku”), it is called a “tanto.”

“Aikuchi,” on the other hand, is a form of koshirae (i.e., mounting style) commonly (but not exclusively) used for tanto. Here, the word “ai” is a gerund that means “to meet” or “meeting,” and “kuchi” is a noun that means “mouth” (i.e., koi-guchi, in this context). So, “aikuchi” style mount means a style of koshirae in which the “fuchi” meets flush with the “koi-guchi.”

The “aikuchi” style mount (=koshirae) can be and was in fact used not only for tanto, but also for wakizashi and katana blades. [Historically, there were quite a few (but not very many) katana and many hira-zukuri wakizashi mounted in the “aikuchi” style.] However, what may be confusing is that because the “aikuchi” style mount was stereo-typically and significantly common to tanto when those who are “in the knows” simply say an “aikuchi,” it almost always means an “aikuchi style tanto” unless otherwise noted.

Now, “hamidashi” can be an adjective meaning “protruding” or a past participle meaning “protruded.” Therefore, a “hamidashi” style tanto is a tanto mounted in a koshirae with a very small tsuba whose edges are only a little bit protruding from the tsuka and saya. In Nihon-to jargon, “hamidashi” can refer to a style of koshirae as well as a style of tsuba designed exclusively for tanto to be mounted in the “hamidashi” style koshirae.

As for “shaku,” it is an old Japanese unit for length that equals 30.3cm (set by the law). Traditionally, tanto was *normally* made less than one “shaku” in nagasa. However, there are also quite a few tanto blades that are slightly longer than one “shaku” in nagasa.

Those “oddball” tanto are called “sun-nobi” tanto. Here, “sun” is an lower unit of length in the same old Japanese unit system: One “sun” equals 3.03cm. However, the word “sun” is also used as noun meaning “a little bit in length” or “very small length.” (Much like the word “bit” in English.)

“Nobi” is a gerund meaning “extending” or a past participle meaning “extended.” Therefore, even though those “sun-nobi” tanto may not have the blades that are exactly one “sun” (i.e., 3.03cm) longer than the conventional maximum length of one “shaku” (i.e., 30.3cm), they are still called “sun-nobi” tanto because they are “a little bit longer” than the standard tanto length.

On the side note, under the current Japanese legal classification, a “tanto” is defined as a traditionally made edged weapon whose blade nagasa is exactly 30cm or less, instead of 30.3cm or less."

S. Alexander Takeuchi, Ph.D. (aka Dr. T)
Department of Sociology
University of North Alabama