For the most part, an attache case and a briefcase are practically interchangeable - but when you compare them side by side, they do have unique histories and some distinctive qualities.
The word attache was coined by the French. It refers to an administrative member of an ambassador’s staff. Ambassadors and their staff carried their papers and documents in slim cases that became known as attache cases.
The word briefcase has its roots in the legal field. A brief is a summary of facts and legal positions supporting arguments in judicial proceedings. Lawyers carried their briefs in a case. Thus, briefcase.
An attache case is a small, thin suitcase used especially for carrying papers and documents but can also carry a laptop. It opens into two distinct compartments that are usually symmetrical. Attache cases have a leather or metal exterior and a slim profile.
A briefcase is also a flat, rectangular container, and is generally used for carrying books, papers, and laptops. It opens into one primary compartment and then has a “lid” that may have pockets or gussets that expand to hold other items. Briefcases are typically made of leather, and are bulkier compared to an attache case, allowing for more or larger contents.
When you compare an attache case and a briefcase, the differences are subtle. But, depending on your style preference or your functionality needs, those slight differences could end up mattering quite a lot.