Anglo-Norman 'walet' (a travel pack) — narrowed from pilgrim's bag to money pouch to flat folding case.
A pocket-sized flat folding case for holding money, cards, and other small flat objects.
From Anglo-Norman French 'walet' (a pack, a knapsack, a traveler's bag, a pilgrim's satchel), of uncertain further origin — possibly from Proto-Germanic *wall- (to roll, to fold), possibly from a Celtic source, or from Medieval Latin 'valesia' (a type of bag). The original meaning was a large bag or knapsack, the kind a pilgrim, shepherd, or traveling merchant would carry over the shoulder — not the small, flat money-holder we know today. The semantic narrowing from 'travel bag' to 'money pouch' to the modern flat folding
A 'wallet' was originally a knapsack — a large bag carried on a journey, containing food and clothing. Chaucer mentions wallets in this sense. The narrowing from 'travel bag' to 'money holder' occurred over several centuries as people needed a word for the increasingly common practice of carrying paper money and identity documents in a small, portable container.