counter for articles
箇 is a specialized counter used for enumerating articles, items, or things. Its meaning is purely grammatical: it marks a unit of something being counted.
箇 combines 竹 (bamboo) with 固 (hard, solid). Historically, bamboo strips were used for counting or record-keeping, and 固 may have reinforced the idea of individual solid items. The exact development is uncertain.
Bamboo 竹 strips tied together with a solid 固 knot make a handy counter for articles. Each strip is one item.
For カ, imagine a counter made of bamboo that goes 'ka-chunk' each time you count an article: ka -> カ.
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place; point; part; spot; area; passage; portion
item; article; clause; section; point
counter used with Sino-Japanese words
one year
one place; (all in) the same place; one spot; one location; one part; one passage
septennial; recurring every seven years
triennial
tied-up places (spots)
novennial; recurring every nine years
The Twenty-One Demands
biennial
two places; two spots; two locations; two parts; two passages
quinquennial; recurring every five years
Charter Oath (of the Meiji Emperor); Five-Point Imperial Covenant; Imperial Oath of Five Articles
articles of faith
88 temples (of, or modeled after those of, Shikoku)
octennial; recurring every eight years
sexennial; recurring every six years
decennial; recurring every ten years
88 temples of Shikoku (holy spots related to Kobo Daishi)