Rummage means to search for something, but in a scattered, disorganized manner. You can rummage through your drawer looking for a lost sock, or you could even hold "a rummage sale" to sell off all your socks that are missing their mates.
Ahoy, mateys: the word rummage hails from a sea-faring background. The Middle Dutch ruim, Germanic rum, and Old English rum all referred to a compartment on a ship, probably stemming from the Middle French verb arrumer, "to stow goods in the hold of a ship." The idea of rummaging as searching was first recorded in the 1620s. The first rummage sale also had its ship connection, as it was a sale on the docks of unclaimed items.