also: エコバック · エコ・バッグ · エコ・バック
noun
eco bag; reusable shopping bag
A reusable bag, typically made of cloth or sturdy plastic, carried to reduce single-use plastic bag consumption.
買い物に行くときはいつもエコバッグを持っていく。
I always take an eco bag when I go shopping.
レジ袋が有料になってから、エコバッグを使う人が増えた。
Since plastic shopping bags became chargeable, more people have started using reusable bags.
マイバッグ is a synonym for エコバッグ, often used in campaigns encouraging shoppers to bring their own bags.
Wasei-eigo (Japanese-made English) combining 'eco' (ecological) and 'bag'. The irregular variant エコバック likely arose from the similar pronunciation of 'bag' and 'back' in Japanese.