The only free and comprehensive online etymological dictionary of the Spanish language
mente m. (Noun) "mind"
10th cent. Old Spanish miente. From Latin mentem, accusative of mens 'id.' From Proto-Italic *mn̥ti- 'id.' From Proto-Indo-European *mn̥-ti- 'id.' From the root *men- "to think."
Indo-European
Romance
Portuguese mente, Catalan ment, Italian mente, Aromanian minti, Romanian minte, Sardinian mente
Germanic
Gothic ga-minþi "memory," Old Norse mynd "image," Old High German gi-munt "memory," Old English ge-mynd "mind" (English mind)
Balto-Slavic
Old Church Slavonic pamętь "memory," Russian pá-mjat' 'id.,' Czech pamět' 'id.,' Slovene pámet, Lithuanian mintìs "idea"
Indo-Iranian
Sanskrit matí- "thought," "mind"

For the origin of the word as a suffix, see -mente.