late 14c., "completely;" early 15c., "in a straight line," also, figuratively (of speaking or writing) "clearly, unmistakably, expressly," from direct (adj.) + -ly (2). Meaning "at once, straightway, immediately in time" (c. 1600) is from earlier sense of "without intermediate steps" (1520s).
he was directly responsible
these two factors are directly related
measured the physical properties directly
the path leads directly to the lake
he didn't answer directly
diptych
dire
direct
direction
directive
directly
directness
director
directorate
directorial
directorship