Why small version of katakana ヵ is used in a word 二ヵ国語


Why do they use sometimes small version of katakana ヵ 'ka' in a word 二ヵ国語
(nikakokugo -bilingual)?

For me, more intuitive form could be 二か国語. Katakana characters in small forms
other than ya, yu, yo, shi + vowels should not even exist. ;)

Is there any significant reason for it?




### Main question: _Why do they use sometimes small version of katakana ヵ 'ka'
in a word?_

The small ヵ here actually derives from the kanji 個 or 箇, used as the generic
counter for things. This was abbreviated to 个, and in turn, this became the
regular-sized ケ or small ヶ seen in words like 一ヶ月. Since the counter in these
contexts is read as _ka_ , this abbreviated kanji form ヶ came to be written
using the alternate small katakana ヵ, probably to match the phonetics, and
possibly to avoid potential confusion in readings with the actual katakana ケ.

So the reason would be gradual historical development. (As with most odd
things in languages.)

### Side question: _Why do katakana characters in small forms other than ya,
yu, yo, shi + vowels even exist?_

There's the historical development reason above, for small kana used in
Japanese.

Past there, kana are actually used for more than just Japanese -- they are
also used to write Ainu. Ainu has final consonants, and the small-kana
variants are used to indicate these. For instance, the word _sir_ in Ainu
means "place, land, country; mountain", and this is spelled in katakana as シㇼ
with the small ㇼ to indicate the final `/r/` sound. [See this Wikipedia
article for more about small katakana used to write
Ainu](https://en.wikipedia.org/wiki/Ainu_language#Special_katakana_for_the_Ainu_language).




### Main question: _Why do they use sometimes small version of katakana ヵ 'ka'
in a word?_

The small ヵ here actually derives from the kanji 個 or 箇, used as the generic
counter for things. This was abbreviated to 个, and in turn, this became the
regular-sized ケ or small ヶ seen in words like 一ヶ月. Since the counter in these
contexts is read as _ka_ , this abbreviated kanji form ヶ came to be written
using the alternate small katakana ヵ, probably to match the phonetics, and
possibly to avoid potential confusion in readings with the actual katakana ケ.

So the reason would be gradual historical development. (As with most odd
things in languages.)

### Side question: _Why do katakana characters in small forms other than ya,
yu, yo, shi + vowels even exist?_

There's the historical development reason above, for small kana used in
Japanese.

Past there, kana are actually used for more than just Japanese -- they are
also used to write Ainu. Ainu has final consonants, and the small-kana
variants are used to indicate these. For instance, the word _sir_ in Ainu
means "place, land, country; mountain", and this is spelled in katakana as シㇼ
with the small ㇼ to indicate the final `/r/` sound. [See this Wikipedia
article for more about small katakana used to write
Ainu](https://en.wikipedia.org/wiki/Ainu_language#Special_katakana_for_the_Ainu_language).

