Word Study
ago
CIDE DICTIONARY
ago, a. & adv. [OE. ago, agon, p. p. of agon to go away, pass by, AS. āgān to pass away; ā- (cf. Goth. us-, Ger. er-, orig. meaning out) + gān to go. See Go.].
Past; gone by; since; as, ten years ago; gone long ago. [1913 Webster]
OXFORD DICTIONARY
ago, adv. earlier, before the present (ten years ago; long ago).
Usage
Note the construction it is ten years ago that (not since) I saw them.
Etymology
ME (ago, agone), past part. of obs. ago (v.) (as A-(2), GO(1))
THESAURUS
ago
antiquated, antique, back, back when, backward, blown over, by, bygone, bypast, dated, dead, dead and buried, deceased, defunct, departed, elapsed, expired, extinct, finished, forgotten, gone, gone by, gone glimmering, gone-by, has-been, into the past, irrecoverable, lapsed, no more, obsolete, over, passe, passed, passed away, past, reminiscently, retroactively, retrospectively, run out, since, vanished, wound upROGET THESAURUS
ago
The Past
N the past, past time, days of yore, times of yore, days of old, times of old, days past, times past, days gone by, times gone by, bygone days, old times, ancient times, former times, fore time, the good old days, the olden time, good old time, auld lang syne, eld, antiquity, antiqueness, status quo, time immemorial, distance of time, remote age, remote time, remote past, rust of antiquity, paleontology, paleography, paleology, paleozoology, palaetiology, archaeology, paleogeography, paleoecology, paleobotany, paleoclimatoogy, archaism, antiquarianism, medievalism, Pre-Raphaelitism, paleography, retrospect, retrospection, looking back, memory, laudator temporis acti, medievalist, Pre-Raphaelite, antiquary, antiquarian, archmologist, Oldbuck, Dryasdust, ancestry, past, gone, gone by, over, passed away, bygone, foregone, elapsed, lapsed, preterlapsed, expired, no more, run out, blown over, has-been, that has been, extinct, antediluvian, antebellum, never to return, gone with the wind, exploded, forgotten, irrecoverable, obsolete, former, pristine, quondam, ci-devant, late, ancestral, foregoing, last, latter, recent, over night, preterperfect, preterpluperfect, looking back, retrospective, retroactive, archaeological, paleo-, archaeo-, formerly, of old, of yore, erst, whilom, erewhile, time was, ago, over, in the olden time, anciently, long ago, long since, a long while, a long time ago, years ago, yesteryear, ages ago, some time ago, some time since, some time back, yesterday, the day before yesterday, last year, ultimo, lately, retrospectively, ere now, before now, till now, hitherto, heretofore, no longer, once, once upon a time, from time immemorial, from prehistoric times, in the memory of man, time out of mind, already, yet, up to this time, ex post facto, time was, the time has been, the time hath been, you can't go home again, fuimus Troes, fruit Ilium, hoc erat in more majorum, O call back yesterday, bid time return, tempi passati, the eternal landscape of the past, ultimus Romanorum, what's past is prologue, whose yesterdays look backward with a smile, Time with reference to a particular period.For further exploring for "ago" in Webster Dictionary Online