"unload, relieve oneself of," 1850, from off (adv.) + load (v.). Originally South African, on the model of Dutch afladen.
Entries linking to off-load
off prep., adv.
by c. 1200 as an emphatic form of Old English of (see of), employed in the adverbial use of that word. The prepositional meaning "away from" and the adjectival sense of "farther" were not firmly fixed in this variant until 17c., but once they were they left the original of with the transferred and weakened senses of the word. Meaning "not working" is from 1861.
Off the cuff "extemporaneously, without preparation" (1938) is from the notion of speaking from notes written in haste on one's shirt cuffs. In reference to clothing, off the rack (adj.) "not tailored, not made to individual requirements, ready-made" is by 1963, on the notion of buying it from the rack of a clothing store; off the record "not to be publicly disclosed" is from 1933; off the wall "crazy" is 1968, probably from the notion of a lunatic "bouncing off the walls" or else in reference to carom shots in squash, handball, etc.
load v.
late 15c., "to place in or on (a vehicle)," from load (n.). Sense of "add to the weight of, put a load in or on" is from c. 1500; sense of "to charge a firearm" is from 1620s. Intransitive sense "put or take on a load or charge" is from 1720; of a vehicle, "to fill with passengers," from 1832. Of computer files or programs, by 1977. Related: Loaded; loaden (the old strong past participle, persisting till 18c. in poetry but now obsolete); loading.