There's a documentary show called Taboo, which i haven't seen in years but was the first thing i thought of for this theme. The general premise of the show is some things are forbidden, disgusting, or just plain weird to our culture but normal, everyday, or downright required for others. One episode covered rites of passage - everything from facial tattoos to something i'm not sure i can describe accurately, but it involved bulls and lots of running, and not the logical away-from-the-bulls running you'd normally think of.
One particular rite of passage took place near one of the major rivers in Africa. The tribe living there believed crocodiles were incredibly powerful (okay, who doesn't?), but they also believed making themselves look like a particular animal would imbue them with the power of said animal. For a boy to be considered a man, he had to submit to being covered with cuts meant to resemble crocodile scales; then he and the other boys going through the ritual would temporarily move into a hut which would be constantly filled with smoke, designed to irritate the cuts as they healed so they would be guaranteed to form clear scars.
For my faeries, i imagine a hunting tribe passing down the idea of the dangerous fae-eating snakes from the times before St. Patrick drove them out of Ireland, who still insist anyone who wants to be considered a proper hunter (or huntress) must alter emself to have the appearance of snakeskin. The real old-school traditionalists go so far as to bind their legs in imported snakeskin whenever they aren't busy cutting up said legs.