From 纏(まと)め (matome, “連(れん)用(よう)形(けい) (ren'yōkei, “stem or continuative form”) of the verb 纏(まと)める (matomeru).”) + 髪(かみ) (kami).
まとめがみ • (matomegami) ←まとめがみ (matomegami)?