1590s, "not understood;" 1610s, "not taken or arrested," from un- (1) "not" + past participle of apprehend (v.).
Entries linking to unapprehended
un- 1
prefix of negation, Old English un-, from Proto-Germanic *un- (source also of Old Saxon, Old Frisian, Old High German, German un-, Gothic un-, Dutch on-), from PIE *n- (source of Sanskrit a-, an- "not," Greek a-, an-, Old Irish an-, Latin in-), combining form of PIE root *ne- "not." Often euphemistic (such as untruth for "lie").
The most prolific of English prefixes, freely and widely used in Old English, where it forms more than 1,000 compounds. It underwent a mass extinction in early Middle English, but emerged with renewed vigor 16c. to form compounds with native and imported words. It disputes with Latin-derived cognate in- (1) the right to form the negation of certain words (indigestable/undigestable, etc.), and though both might be deployed in cooperation to indicate shades of meaning (unfamous/infamous), typically they are not.
It also makes words from phrases (such as uncalled-for, c. 1600; undreamed-of, 1630s; uncome-at-able, 1690s; unputdownable, 1947, of a book; un-in-one-breath-utterable, Ben Jonson; etc., but the habit is not restricted to un-; such as put-up-able-with, 1812). As a prefix in telegramese to replace not and save the cost of a word, it is attested by 1936.
apprehend v.
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.