abandon (n.) Look up abandon at Dictionary.com
"a letting loose, freedom from self-restraint, surrender to natural impulses," by 1822 as a French word in English (it remained in italics or quotation marks through much of the 19c.; the naturalized abandonment in this sense was attempted from 1834), from a sense in French abandon "abandonment; permission" (12c.), from abandonner (see abandon (v.)).

The noun was borrowed earlier (c. 1400) from Old French in a sense "(someone's) control;" and compare Middle English adverbial phrase at abandon, i.e. "recklessly," attested from late 14c. In Old French, the past participle adjective abandoné came to mean "zealous, eager, unreserved."
abandon (v.) Look up abandon at Dictionary.com
late 14c., "to give up (something) absolutely, relinquish control, give over utterly;" also reflexively, "surrender (oneself), yield (oneself) utterly" (to religion, fornication, etc.), from Old French abandoner "surrender, release; give freely, permit," also reflexive, "devote (oneself)" (12c.).

The Old French word was formed from the adverbial phrase à bandon "at will, at discretion," from à "at, to" (from Latin ad; see ad-) + bandon "power, jurisdiction," from Latin bannum, "proclamation," which is from a Frankish or other Germanic word, from Proto-Germanic *bannan- "proclaim, summon, outlaw" (things all done by proclamation); see ban (v.).
Mettre sa forest à bandon was a feudal law phrase in the 13th cent. = mettre sa forêt à permission, i.e. to open it freely to any one for pasture or to cut wood in; hence the later sense of giving up one's rights for a time, letting go, leaving, abandoning. [Auguste Brachet, "An Etymological Dictionary of the French Language," transl. G.W. Kitchin, Oxford, 1878]
Meaning "to leave, desert, forsake (someone or something) in need" is from late 15c. (Etymologically, the word carries a sense of "put (something) under someone else's control.") Earliest appearance of the word in English is as an adverb (mid-13c.) with the sense "under (one's) control," hence also "unrestricted." Related: Abandoned; abandoning.