The reefer is a knee length beltless overcoat with a single row of buttons. Not thin like a trenchcoat, but of heavier material, typically wool. Named for the fishermen who fished off the reefs and wore such jackets in typically miserable weather. Also my last name, being descended, I guess, from such fishermen. As for the doobie's namesake, a reef is a horizontal section of sail, which when rolled up, looks like a giant doobie.