Proto-Indo-European Roots

Root/Stem: *[email protected]ér-
Meanings:  a daughter
Hellenic Greek thugatér (a daughter)
Celtic Gaulish duxtir (a daughter), Old Irish der- (in composite names)
Indic Sanskrit duhitá-, duhitar- (a daughter)
Dardic & Nuristani Khowar zhur (a daughter), Prasun lušt (a daughter)
Iranian Avestan [email protected] (a daughter), 
Persian duxtar, duxt
Tocharian Tocharian A ckacar, Tocharian B tkac'er (a daughter)
Armenian dustr (a daughter), gen. dster
Germanic Common Germanic *doxtir (a daughter), >
Gothic dauhtar, Old English & Old Saxon dohtor, Runic Scandianvian dohtriR (nom. pl.), Old Icelandic dóttir, Old High German tohter, Old Frisian dochter
Swedish dotter, German Tochter, Scots dochter
Baltic Lithuanian dukte. (a daughter), Old Prussian duckti, Sudovian dukté
Slavic Common Slavic *dütjí (a daughter), >
Ukrainian doch, Old Church Slavonic düshti, Serbo-Croatian kchi, Bulgarian [email protected]'a, Slovene hc'i, hc'erka, Old Czech dci, Czech & Slovak dcera, Polish cora, Russian doch'
Notes: The etymology of this word seems rather dark, unlike that of the previous ones: 'father, mother, sister'. It is the last in the series shaped by the suffix -er and therefore belonging to r-stem nouns.
A few branches replaced this stem by another one, for instance Italic and Celtic, again for unknown reasons.
The unstressed vowel of the second syllable is the Indo-European 'schwa' which was dropped in Armenian, Germanic, Baltic, Slavic, and Iranian languages.