apprehensive adj.

late 14c., apprehenden, "grasp with the senses or mind;" early 15c., "grasp, take hold of" physically, from Latin apprehendere "to take hold of, grasp," from ad "to" (see ad-) + prehendere "to seize." This is from prae- "before;" see pre- + -hendere, from PIE root *ghend- "to seize, take."

The metaphoric extension to "seize with the mind" took place in Latin and was the sole sense of cognate Old French aprendre (12c., Modern French appréhender). Often "to hold in opinion but without positive certainty."

We "apprehend" many truths which we do not "comprehend" [Richard Trench, "On the Study of Words," 1856] 

Also compare apprentice). The specific meaning "seize in the name of the law, arrest," is from 1540s. The meaning "be in fear of the future, anticipate with dread" is from c. 1600. Related: Apprehended; apprehending.