"remove the cargo from," Old English onhladen; see un- (2) "reverse, opposite of" + lade (v.). Related: Unladen; unlading.
Entries linking to unlade
un- 2
prefix of reversal, deprivation, or removal (as in unhand, undo, unbutton), Old English on-, un-, from Proto-Germanic *andi- (source also of Old Saxon ant-, Old Norse and-, Dutch ont-, Old High German ant-, German ent-, Gothic and- "against"), from PIE *anti "facing opposite, near, in front of, before, against" (from PIE root *ant- "front, forehead," with derivatives meaning "in front of, before").
More or less confused with un- (1) through similarity in the notions of "negation" and "reversal;" an adjective such as unlocked might represent "not locked" (un- (1)) or the past tense of unlock (un- (2)).
lade v.
Old English hladan (past tense hlod, past participle gehladen) "to load, heap up, burden" (the general Germanic sense), also "to draw or take up water" (a meaning peculiar to English), from Proto-Germanic *hlathan- (source also of Old Norse hlaða "to pile up, load, especially a ship," Old Saxon hladan, Middle Dutch and Dutch laden, Old Frisian hlada "to load," Old High German hladen, German laden), from PIE *klā- "to spread out flat" (source also of Lithuanian kloti "to spread," Old Church Slavonic klado "to set, place").
In modern use restricted to the loading of ships; past participle laden was active in the language longer, but in 20c. was displaced by loaded (but a distinct word in the literal sense would be useful) except in particular phrases. Compare Lading.