To bring a held thing from elsewhere onto one's own ground. The crossing that makes a copy yours.
Old English dūn (hill, later off the hill, downward) plus lād (a course, a way, later a burden carried); a twentieth-century pairing for pulling a held thing onto one's own ground.
The bringing of a held thing from elsewhere onto ground of one's own. What crosses in a download becomes a copy that belongs to whoever received it.