古英語の*Ēastreと古高ドイツ語の*Ôstaraは同義語であり、共通の起源を持つ言語的な兄弟である。これらは原ゲルマン語の同名異義語*Austrō(n)に由来し<ref>Simek, 1996, p74</ref><ref>Kroonen, 2013, p43</ref>、それ自体が「(赤く)輝く」という意味のPIE語源*h₂ews-から拡張した原インド・ヨーロッパ語(PIE)*h₂ews-reh₂-(参照:バルト語 *auš(t)ra 『夜明け、朝』)の派生とされている<ref name="WATKINS-2021">Watkins 2006 [2000]: 2021.</ref><ref>Kroonen, 2013, p43</ref>。現代英語のeastもこの語源に由来し、原始ゲルマン語の副詞*aust(e)raz(「東、東方」)を経て、それ以前のPIE *h₂ews-tero- (「東、夜明けに向かって」)<ref>Kroonen, 2013, p43</ref>に由来している。
言語学者グース・クローネンによると、ゲルマン語とバルト語は、「夜明けの女神」の名前である古い形の*h₂éws-osを、リトアニアの神Aušrinėに見られるような-reh₂-に置き換えたとのことだ<ref>Kroonen, 2013, p43</ref>。アングロ・サクソンのイングランドでは、彼女の春の祭りは、4月に相当する月(北部サクソン語:Ēosturmōnaþ, 西サクソン語:Eastermonað)<ref>Sermon, 2008, p333</ref>に名前を与え、その後、キリスト教のイースターの祭りがそれに取って代わった<ref>Simek, 1996, p74</ref><ref>West, 2007, pp217–218</ref>。中世ドイツ南部では、Ôstarûnという祭りがÔstarmânôthという月と現代のOstern(復活祭)の名前になったのと同様に、オスタラ(Ôstara)という女神がそこで崇拝されていたことが示唆される<ref>Simek, 1996, p255</ref><ref>West, 2007, pp217–218</ref>。この月の名前は、18世紀のドイツ語に「Ostermonat(オステルモナート)」として残っている<ref>Sermon, 2008, p335</ref>。古サクソン語で春の女神に相当する *Āsteron も、ほとんどの学者が「復活祭の家」と訳している asteronhus という用語から再構築することができる(中世フラマン語の Paeshuys 「復活祭の家」参照)<ref>Sermon, 2008, "この用語は「東部の家」または「復活祭の家」のどちらかを意味するが、現在の研究ではこの2つの読みのうち後者を支持する傾向がある(Hessmann 2000)。この解釈は、フランドル地方の地名・姓である「Paashuis」または「Paeschhuis」(「復活祭の家」の意)とも類似しており、最も古い例は1386年のアントワープでの記録「Paeshuys」である(Debrabandere 1993: 1073)。", pp337–338</ref>。
According to linguist Guus Kroonen, the Germanic and Baltic languages replaced the old formation *''[[H₂éwsōs|h₂éws-os]]'', the name of the PIE [[Dawn goddess|dawn-goddess]], with a form in ''-reh₂''-, likewise found in the Lithuanian deity ''[[Aušrinė]]''. In [[Anglo-Saxon England]], her springtime festival gave its name to a month (Northumbrian: ''{{lang|ang|Ēosturmōnaþ}}'', West Saxon: ''Eastermonað''), the equivalent of April, then to the Christian feast of ''[[Easter]]'' that eventually displaced it. In southern Medieval Germany, the festival ''Ôstarûn'' similarly gave its name to the month ''Ôstarmânôth'', and to the modern feast of ''Ostern'' ('Easter'), suggesting that a goddess named *''Ôstara'' was also worshipped there. The name of the month survived into 18th-century German as ''Ostermonat''. An [[Old Saxon]] equivalent of the spring goddess named *''Āsteron'' may also be reconstructed from the term ''asteronhus'', which is translated by most scholars as 'Easter-house' (cf. [[Middle Dutch|Medieval Flemish]] ''Paeshuys'' 'Easter-house').{{Sfn|Sermon|2008|ps=: "The term ''asteronhus'' could mean either 'Eastern-house' or 'Easterhouse', although current research tends to favor the latter of these two readings (Hessmann 2000). This interpretation is paralleled in the Flemish place-name and surname ''Paashuis'' or ''Paeschhuis'', also meaning 'Easter-house', of which the earliest known example is ''Paeshuys'' recorded at Antwerp in 1386 (Debrabandere 1993: 1073)."|pp=337–338}} Frankish historian [[Einhard]] also writes in his ''[[Vita Karoli Magni]]'' (early 9th c. AD) that after [[Charlemagne]] defeated and converted the continental Saxons to Christianity, he gave Germanic names to the Latin months of the year, which included the Easter-month ''Ostarmanoth''.{{Sfn|Sermon|2008|p=334}}
The Old English {{lang|ang|Ēostre}} is therefore a distant cognate of numerous other dawn goddesses attested among Indo-European-speaking peoples, including [[Ushas|Uṣás]], [[Eos|Ēṓs]], and [[Aurora (mythology)|Aurōra]]. In the words of the ''[[Encyclopedia of Indo-European Culture]]'', "a Proto-Indo-European goddess of the dawn is supported both by the evidence of cognate names and the similarity of mythic representation of the dawn goddess among various [[Indo-European languages|Indo-European]] groups. [...] All of this evidence permits us to posit a Proto-Indo-European *''{{PIE|[[hausos|h<sub>a</sub>éusōs]]}}'' 'goddess of dawn' who was characterized as a 'reluctant' bringer of light for which she is punished. In three of the Indo-European stocks, [[Baltic languages|Baltic]], [[Greek language|Greek]] and [[Indo-Iranian languages|Indo-Iranian]], the existence of a Proto-Indo-European 'goddess of the dawn' is given additional linguistic support in that she is designated the 'daughter of heaven'."{{sfn|Mallory|Adams|1997|pp=148–149}}