From 絞(しぼ)り (shibori, “wringing, 連(れん)用(よう)形(けい) (ren'yōkei, “stem or continuative form”) of the verb 絞(しぼ)る (shiboru).”) + 袋(ふくろ) (fukuro, “bag”).
しぼりぶくろ • (shibori-bukuro) ←しぼりぶくろ (siboribukuro)?