Brawn (varies)
The brawn quirk is a measure of how solidly your character is built; brawnier characters will tend to be stronger, will be able to perform physically demanding tasks for an extended period of time before they become fatigued, and recover more quickly from illness, injury, or fatigue.
If you are planning to go on lots of expeditions to far-off lands, you should certainly consider taking this quirk: you don't want to slow your party down because you're out of breath, after all.
Weak (-1): The big kids picked on you when you were small. Come to think of it, they may well still be picking on you. You are the man in the "before" picture in the Charles Atlas adverts - you know, the guy who gets sand kicked in his face by beach bullies. You are either weedy or just plain out of shape.
Average (0): All characters are assumed to have this level of Brawn unless they specify otherwise. You are perfectly normal.
Well-Built (2): You're in shape, but you're no bodybuilder. Perhaps you've been working on the docks for a while; certainly, you are strong enough and have enough endurance to spend your day moving heavy packing crates around.
Does This Guy Ever Stop? (4): You are the "after" picture in the Charles Atlas adverts, only you don't take as many steroids. You are really quite strong, although if you are not a skilled fighter this won't necessarily help you in a scrap. What's really impressive is your endurance: you are like the Energiser bunny of strenuous physical labour. When you go on expeditions, people may end up using you as a pack mule.