I am the bone of my sword is the first line of the incantation, that summons the reality marble of Shirou Emiya and Archer in the Type-Moon Fate series.
The incantation grew popular with fans of the series and has been turned into the matter of parodies and copypasta online.
The Fate series of Type Moon started with the 2004 visual novel game, titled Fate/stay night, which features the Unlimited Blade Works, the reality marble of Shirou Emiya.
“I am the bone of my sword” appears in the incantations of both Shirou Emiya and Archer, who use the incantation to summon their reality marbles.
“I am the bone of my sword” would reemerge in various conversations and threads online, from sites like Tumblr, Reddit and 4chan to Gamefaqs and TVTropes.
The quote appeared in an Urban Dictionary entry as well, which is explaining the meaning behind Unlimited Blade Works.
Both the movie and anime adaptations of Fate/stay night boosted the popularity of “I am the bone of my sword”.
- Type-Moon Fandom – Unlimited Blade Works