word-forming element meaning "all," from Latin omni-, combining form of omnis "all, every, the whole, of every kind," a word of unknown origin, perhaps literally "abundant," from *op-ni-, from PIE root *op- "to work, produce in abundance."
late 14c., direccioun, "action of directing or guiding," from Latin directionem (nominative directio) "a making straight, a straight line, a directing (toward something)," noun of action from past-participle stem of dirigere "to set straight, arrange; give a particular direction to," from dis- "apart" (see dis-) + regere "to direct, to guide, keep straight" (from PIE root *reg- "move in a straight line").
Meaning "the act of governing, administration" is from early 15c. Sense of "relative position without regard to distance" is from 1660s. Meaning "course pursued by a moving object" is from 1660s.
Sense of "order, instruction in how to proceed" is from early 15c.; specific sense of "instruction in how to get somewhere" is from 1590s (directions in this sense is by 1749). Related: Directional.