1510s, "in a straight line," from direct (adj.) + -ly (2). Figurative use is slightly earlier (c. 1500). Meaning "at once, immediately in time" (c. 1600) is from earlier sense of "without intermediate steps" (1520s).
1. She went directly to Simon's apartment and knocked on the door.
2. Catherine saw to it that the information went directly to Walter.
3. An elevator mechanic can work the machinery directly by turning this lever.
4. This was a straight conflict of directly opposed aims.
5. Luke sat directly behind the pilot and conversed with him.