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 Narabini Hyakuin (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.
Female ninja are mentioned in Bansenshukai, a 17th-century Japanese book compiling the knowledge of the clans in the Iga and Kōga regions devoted to the training of ninja. According to this document, the primary function of female ninja was espionage, finding legitimate service positions in the households of enemies, to accumulate knowledge by gaining trust or overhearing conversations, and facilitate assassinations if needed. One historically accepted example of this is Mochizuki Chiyome, the 16th century noblewoman with ninja roots who was tasked by the warlord Takeda Shingen with recruiting women to create a secret network of a few hundred female spies.
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While well trained in the arts of combat, Kunoichi typically would rely more on seduction if they had the duty to assassinate. They often used small compact weapons to hide in a kimono wore over more practical clothing. For example, dagger-like hairpins, and the neko te were "cat claws" that would be stabbed into a target's neck and would sometimes be dipped in venom before use.Tessen, metal bladed folding fans, were also in use as they can be a "weapon hid in plain sight" because tessen were carried around by everyone in the era. Kunoichi were known to use vials of poison on a targets alcohol, which would result in quick consumption and potency. When a kunoichi was discovered or harmed screaming while shedding their kimono before running away would allow discomfort and confusion in the target while misdirecting attention.