The language of Attire does more than allow us to speak our minds in a personalized visual sense; it also operates as a banner that announces, and sometimes carries forward, broader social change. Its difficult, maybe even impossible for folk under 40 to really understand what a huge shake up women's clothing went through in the 20th century. From our 21st century perspective, the notion of women in pants, man tailored shirts, jackets, and coats is one that is a common part of the daily wear of many women, and seeing anyone dressed that way would inspire almost no negative comment whatever.
Before the 18th century, women dressing as men in any way was virtually unheard of. Where the change began, was the slow creeping influence of military and riding clothing shapes into women's clothing. Aping the color and decorations of men's military wear, especially during a time of war could get a lady by as being patriotic, or supportive of her husband. And through the offices of royal ladies like Sophie Marie here, menswear inspired riding clothes became first a shocking challenge, and then an accepted part of any stylish ladies wardrobe.
Once we got into the 19th century shake ups came more often, and with greater impact. During the mid to late 19th century a movement called the Dress Reform Movement was trying with some success, actually, to get both women and men to dress with more sense and practicality. It was from this movement, (about which I'll post another time in more detail), that the Bloomer Girls emerged.
By the beginning of the 20th century, edgy couturiers like Poiret were designing harem pants and culottes outfits for women who had style and no fear of reprisals, socially.
The thirties and the film industry in the USA pushed things forward as actors like Dietrich and Hepburn took to wearing full on menswear on a pretty regular basis. It increased the acceptability of it across the board and made it all the more reasonable that when World War two happened, women would think nothing of jumping onto overalls and dungarees to get the job done. They never really ever left them again.