Proto-Indo-European Roots

Root/Stem: *deiwo-
Meanings:  a deity, a god, Daylight god
Cognates (42):
Hellenic Greek dios (a god), Zeus (Zeus), Laconic Deus 
Italic Latin deus < deivus (a god), Juppiter < *Diu-pater, dies (a day), Old Latin Diovis (Jupiter), Oscan diu'vei' (Jupiter;, deivai' (goddess;, Umbrian iupater (Jupiter), di (a god, Jupiter), Paelignan ioviis (Jupiter;, Marrucinian ioues (Jupiter;, Picene iuve (Jupiter;
Celtic  Common Celtic *deiuo-  , > 
Gaulish De'vona, De'vognata, Old Irish di'a (a god, a day), Old Welsh duiu (a deity), Welsh duw, Old Cornish duy, Breton doue, doe (a god), Irish & Scottish Gaelic dia (a god), Di- (a day)
Indic Sanskrit dyauh. (a god, Daylight god), de'vah. (a god) 
Iranian Avestan dae'va- (a demon)
Anatolian Common Anatolian *diu- (daylight god), > 
Palaic tijaz, tiuna (a god), Luwian tiwat (sun god), Lycian ziw (a god), Lydian Divi- (a god), DivNali- (divine)
Germanic Germanic *tiw-, > 
Old Norse ti'war (gods;, Old English Ti'g, Tiwes (War god), Old High German Zio
Baltic  Common Baltic *deiwo-, > 
Lithuanian dievas (a god), Latvian dievs, Old Prussian deiws, deywis (a god), Sudovian deivas
Slavic  Common Slavic *div-, > 
Old Church Slavonic & Ukrainian divo (a wonder), Bulgarian diven (wonderful), Serbo-Croatian divan (wonderful), div (a demon), Czech div (a wonder), Polish dziw, Upper Sorbian dz'iw, Russian divny (wonderful)
Notes: This is believed to have been the name of the principal Indo-European deity, the god of thunder and war, originally the god of daylight. That is why many languages adopted this root to the meaning 'a day' (Celtic, Italic). The only language which translates this stem with a negative meaning is Avestan: Iranians considered *Devas an Aryan deity, and as Aryans are always considered as enemies in Old Iranian mythology, their god acquired the meaning 'a demon'. 
English keeps the stem in the word Tuesday 'the day of Tiw'.