The only free and comprehensive online etymological dictionary of the Spanish language
en (Preposition) "in," "at," "about," "against," "within," "into"
10th cent. From Latin in 'id.' (Archaic Latin en). From Proto-Italic *en 'id.' From Proto-Indo-European *h1en 'id.'
Indo-European
Romance
Portuguese em, Catalan en, French en, Italian in, Aromanian ãn, Romanian în
Italic
Oscan en, Paelignian i
Celtic
Old Irish i, Old Welsh in, Old Breton en, Cornish yn
Germanic
Gothic in, Old Norse í, Old Saxon in, Old High German in, Old English in (English in)
Balto-Slavic
Old Church Slavonic vъn, Russian vo, Lithuanian į, Old Prussian en
Hellenic
Ancient Greek ἐν (en)
Armenian
Armenian i
Tocharian
A yn-, B in-