"one given over to some practice," 1909, first in reference to morphine, from addict (v.).
1530s, "delivered over" by judicial sentence (as a debtor to his creditors, a sense from Roman law); past-participle adjective from addict (v.). The sense of "dependent" (1560s) is reflexive, "self-addicted," from the notion of "give over or award (oneself) to someone or some practice;" specialization to narcotics dependency is from c. 1910. An earlier English adjective was simply addict "delivered, devoted" (1520s).
c. 1600, "tendency, inclination, penchant" (a less severe sense now obsolete); 1640s as "state of being (self)-addicted" to a habit, pursuit, etc., from Latin addictionem (nominative addictio) "an awarding, a delivering up," noun of action from past-participle stem of addicere "to deliver, award; devote, consecrate, sacrifice" (see addict (v.)).
The sense of "compulsion and need to take a drug as a result of prior use of it" is by 1906, in reference to opium (there is an isolated instance from 1779 with reference to tobacco).
c. 1400, "anything added, an increase or increment," from Latin additamentum "an increase," from past-participle stem of addere "to add" (see add).
late 14c., "action of adding numbers;" c. 1400, "that which is added," from Old French adition "increase, augmentation" (13c.), from Latin additionem (nominative additio) "an adding to, addition," noun of action from past-participle stem of addere "add to, join, attach" (see add). Phrase in addition to "also" is from 1680s.
"something that is added" to a chemical solution or food product, 1945, from additive (adj.).
1690s, "tending to be added," from Late Latin additivus "added, annexed," past-participle adjective from Latin addere "add to, join, attach" (see addition). Alternative addititious "additive, additional" (1748) is from Latin additicius "additional."
"become putrid," hence "be spoiled, be made worthless or ineffective," 1640s (implied in addled), from archaic addle (n.) "urine, liquid filth," from Old English adela "mud, mire, liquid manure" (cognate with East Frisian adel "dung," Old Swedish adel "urine," Middle Low German adel "mud," Dutch aal "puddle").
Popularly used in the noun phrase addle egg (mid-13c.) "egg that does not hatch, rotten egg," a loan-translation of Latin ovum urinum, literally "urine egg," which is itself an erroneous loan-translation of Greek ourion ōon "putrid egg," literally "wind egg," from ourios "of the wind" (confused by Roman writers with ourios "of urine," from ouron "urine").
From this phrase, since c. 1600 the noun in English was mistaken as an adjective meaning "putrid," and thence given a figurative extension to "empty, vain, idle," also "confused, muddled, unsound" (1706), then back-formed into a verb in that sense. Related: Addling.
Popular in forming derogatory compounds 17c. and after, such as addle-headed "stupid, muddled" (1660s); addle-pated (1630s); addle-pate "stupid bungler" (c. 1600); addle-plot "spoil-sport, person who spoils any amusement" (1690s).