also over-exposure, "excessive exposure; an excess of exposure," 1834 in reference to cleavage in women's dress; 1855 in photography, from over- + exposure. Figurative sense, in reference to celebrity, is attested from 1969.
word-forming element meaning variously "above; highest; across; higher in power or authority; too much; above normal; outer; beyond in time, too long," from Old English ofer (from PIE root *uper "over"). Over and its Germanic relations were widely used as prefixes, and sometimes could be used with negative force. This is rare in Modern English, but compare Gothic ufarmunnon "to forget," ufar-swaran "to swear falsely;" Old English ofercræft "fraud."
In some of its uses, moreover, over is a movable element, which can be prefixed at will to almost any verb or adjective of suitable sense, as freely as an adjective can be placed before a substantive or an adverb before an adjective. [OED]
Among the old words not now existing are Old English oferlufu (Middle English oferlufe), literally "over-love," hence "excessive or immoderate love." Over- in Middle English also could carry a sense of "too little, below normal," as in over-lyght "of too little weight" (c. 1400), overlitel "too small" (mid-14c.), overshort, etc.
c. 1600, "public exhibition," from expose (v.) + -ure. Sense of "situation with regard to sun or weather" is from 1660s. Photographic sense "act of exposing to light" is from 1839. Indecent exposure attested by 1825.
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Definitions of overexposure from WordNet
the act of exposing film to too much light or for too long a time;
the act of exposing someone excessively to an influencing experience;