Futaro Yamada is the author of many stories about kunoichi and popularized the term.
The term is thought to derive from the names of characters that resemble the three strokes in the kanji character for woman (女 onna?); said in the order they are written: ku (く) - no (ノ) - ichi (一). Early literary quotes include Enshū Senkuzuke Narabi Nihyaku In (遠舟千句附并百韵?) (1680) as well as Maekuzukeshū (前句付集?) (1716), which specifically associates the word with the kanji 女 supporting the etymology of being overpowered. The "くノ一" writing requires the use of one character from each Japanese character set — first hiragana, then katakana, then kanji. While hiragana and kanji can exist in the same word, katakana generally cannot appear in conjunction with the others. There are exceptions to this, for example in "ゴミ箱" and "消しゴム".