From 八(や)つ (yatsu) + 裂(さ)き (saki, “連(れん)用(よう)形(けい) (ren'yōkei, “stem or continuative form”) of the verb 裂(さ)く (saku).”). The saki changes to zaki as an instance of rendaku (連濁).
やつざき • (yatsuzaki) ←やつざき (yatuzaki)?