The only free and comprehensive online etymological dictionary of the Spanish language
daño m. (Noun) "harm," "damage"
12th cent. From Latin damnum 'id.' From Proto-Italic *dapno- "loss." From Proto-Indo-European *dh2p-no- "expenditure." From root *deh2p- "to lose."
Asturian dañu, Portuguese dano, Galician dano, Catalan dany, French dam, Romanian daună, Sardinian dànnu
Old Norse tafn "sacrificial animal"
Armenian tawn "feast"
Akkadian zību, Ugaritic dbḥ, Hebrew zeḇaḥ, Ethiopian zabHa

"In historic times there remains only damnum with the derived sense of “injury sustained, what is taken away by forcible seizure.” It is the expense to which one is condemned by circumstances or by certain legal stipulations. The peasant spirit and the legal exactitude of the Romans transformed the ancient conception: ostentatious expenditure became no more than an outright expenditure, what constitutes a loss." ~ E. Benveniste, Indo-European Language and Society (1973)