Etymology: Probably partly (i) < Anglo-Norman alyé, Anglo-Norman and Middle French alié, allié, allyé (compare Old French alliiet ; French allié ) relative, supporter, associate, friend, also person, state, military force, etc., united or associated with another by league or formal treaty (1297 or earlier in Anglo-Norman; 1316 in Old French as alliiet in specific sense ‘political or military ally’; the precise sense is often difficult to determine in early use; the sense ‘relative’ is only securely attested from 1538), use as noun of past participle of Anglo-Norman and Old French, Middle French alier , Anglo-Norman and Middle French allier , alyer , allyer ally v.; and partly (ii) < ally v.With the Older Scots forms compare allya n. N.E.D. (1884) gives the pronunciation as (ăləi·) /əˈlaɪ/. Both British and U.S. dictionaries of the late 19th and early 20th cent. give the stress on the second syllable as preferred, with first-syllable stress at best a possible alternative, although for evidence that first-syllable stress may have existed already in the 17th cent. compare the metre in quots. 1677 at sense 2b, 1697 at sense 3. D. Jones Eng. Pronouncing Dict. (1922) gives the stress for both the noun and the verb on the second syllable, but notes that the pronunciation of the noun with first-syllable stress ‘appears to be spreading rapidly’. By ed. 8 (1947) of Jones, the now usual stress pattern is in place, with first-syllable stress as the preferred variant. Webster's Third New International Dict. Eng. Lang. (1961) agrees, adding that, in the plural, first-syllable stress is much more frequent. For the verb, second-syllable stress predominates, with first-syllable stress given as a possible alternative in recent pronouncing dictionaries; the exception to this rule is the past participle allied, which Jones (ed. 8, 1947) and later dictionaries record as being usually stressed on the first syllable if used attributively. Some early instances of the word, especially in Older Scots, may show a trisyllabic pronunciation, reflecting the French etymon.

Etymology: < al- (in aluminium n.) + -y suffix⁶.

Etymology: < Anglo-Norman and Old French, Middle French alier, Anglo-Norman and Middle French allier, alyer, allyer (French allier ) (reflexive) to unite oneself or itself to (a person, group of people, or thing) (c1100), to unite, combine, or join in kinship, friendship, association, etc. (c1150 or earlier), to combine or mix (ingredients) (12th cent., originally and chiefly in specific sense ‘to alloy (metals)’; compare discussion at allay v.³; a1394 in a culinary context in allier quelque chose de quelque chose ) < classical Latin alligāre alligate v. Compare Old Occitan aliar (13th cent.), Catalan aliar (1285), Spanish aliar (c1375; rare before 16th cent.), Portuguese aliar (15th cent.), all < French. Compare allay v.³, allay v.¹, alloy v., which show partial semantic overlap with this word (in sense 2), and also alligate v.With the respelling of the prefix, compare the discussion at ad- prefix. With the forms alleye and allay, compare later allay v.³ and the French forms cited at that entry. The stress was originally on the second syllable, and still is today, except for the past participle in attributive use, which is usually stressed on the first syllable (see also note at allied adj.). Recent pronouncing dictionaries record a variant pronunciation with first-syllable stress as an alternative; this may have spread from the past participle in attributive use, and probably also from ally n.¹