if i had to guess, I'd say that what makes some effeminate is a family arrangement with a dominating mother and a passive father,

just to add, i don't see 'camp' necessarily as the opposite of 'effeminate,' unless camp is a term used in the gay community to describe masculine types. If you're family liked going outdoors, and more likely if they liked going on camping trips together, it seems you will be more partial toward doing it when you get older.