This claim may, in fact, have a degree of truth to it. Historically, hakama were made with various numbers of pleats.
The cheapest hakama were made of two panels (that is, made with two widths of cloth, one front, one back) per leg. More common hakama were four-panel hakama, and the fullest and most luxuriant models were made of six panels. The lower number of panels, in addition to limiting the fullness, limited the number of pleats that could be made.
…According to Takada, bushi did not go out in public without wearing hakama over their kosode.1
So, only those of a certain status could afford the higher number of panels and pleats. And bushi (i.e. samurai) always wore a hakama (and presumably a hakama with many pleats) in public. It’s not clear whether the seven pleats were originally intended to represent the seven virtues of Bushido or whether the “seven pleats / seven virtues” relationship evolved organically from the correlation between cost and the number of pleats.
Nevertheless, it’s safe to say that, in martial arts at least, the pleats now represent the seven virtues of Bushido.
Learn more about the hakama and its significance in Aikido in chapter 19 of Principles of Aikido.
- http://www.sengokudaimyo.com/garb/garb.ch01.html ↩