If you look into the history of men's clothing, you'll see that so much of it originated as athletic gear. What we know as the polo shirt was actually invented in 1929 by Rene Lacoste as a tennis shirt. Even Gucci, from 1906 to 1938, was a leather saddlery shop that made high-end equestrian gear before it slowly diversified into a full service fashion house. Maybe men are most comfortable, when they've left the workplace, feeling close to the ball field even when they're not breaking a sweat.

Sometimes the competition-ready origins of these clothes are not so noticeable off the playing field. And on the other hand, clothes like sweatpants, tracksuit tops, tennis sweaters, baseball hats, and even snowboarding jackets have also made their way into the mix of acceptable streetwear. I see dads at my son's school every morning dropping off their kids in Converse All-Stars and their favorite European soccer team sweatshirts. I notice my husband wearing his cricket sweater both on and off the pitch when he's in England. And I even saw Ralph Lauren recently at a formal event wearing jodhpurs with a tuxedo jacket. While it worked on him, I may have to put a "Don't try this at home" label on that one.

Peter O'Toole, always the English gentleman, in a cricket cap. 1990. (credit: Corbis)

Bad boy Dennis Hopper looks unusually classic in his sport jacket layered over a rugby shirt. 1982. (credit: Corbis)

Count Carl von Bismarck exercises his royal entitlement to wear tennis clothes at the lunch table. 1982. (credit: Getty)

I love this guy's Bjorn Borg-inspired tennis shorts. I'm not sure New York City is the best place to wear them--maybe Venice, California or Miami? He looks great nonetheless. Bleecker Street, NYC, June 2007.

Millionaire playboy Gunther Sachs wearing a bobsled team jacket in Saint Moritz. Switzerland, 1970. (credit: Getty)

Two dads at my son's school reconcile early-morning drop-offs with easy-to-throw-on athletic basics such as a soccer sweatshirt and a loose Lacoste tennis shirt. Sullivan Street, NYC, October 2007.

Rod Stewart takes to the street in an Adidas soccer warm-up top. 1983. (credit: Getty)

My brother-in-law Charlie loves to play golf, and he collects shirts from the different courses he plays to wear in his everyday life. Because he's English, I think of him as gentleman jock. Dragon School family picnic, Oxford, England, July 2007.

While it's hard to imagine that Truman Capote actually played any sports, it's clear that he at least wanted to look the part. At home in Long Island, NY, 1965. (credit: Corbis)

This guy caught my interest for wearing basketball sneakers in the most unsportsman like way possible. He looks more like an English D.J. than a basketball player. Bleecker Street, NYC, September 2007.

Although we're used to seeing David Letterman in a double-breasted suit every night, I've heard he is actually a huge fan of sweats, as shown by the customized ones he's wearing here. 1984. (credit: Getty)

My husband, Christopher, hangs around our English cottage in his 20-year-old cricket sweater. Can you tell that he doesn't like having his photo taken? Oxfordshire, England, June 2007.

Bryan Ferry, making a departure from his tailored rock 'n' roll look, yet again confirming the old-school appeal of a cricket sweater. (Just to be clear, what started in England as the cricket sweater became, in America, the tennis sweater.) 1974. (credit: Getty)

I'm sure there will be a great divide on the success of Brad Pitt's look in this early photo of him. I think he looks super-hot, in a tacky eighties teenager sorta way. 1988. (credit: Getty)

Ralph Lauren (with wife Ricky) in jodhpurs and not a horse in sight. CFDA Fashion Fund awards, NYC, November 2007. (credit: Sherly Rabbani and Josephine Solimene)