The only free and comprehensive online etymological dictionary of the Spanish language
mirar (Verb) "to look (at)"
12th cent. meaning "to admire." First attestation with the sense of "to look" occurs in 13th cent. Occuring in toponyms from at least the 7th cent. (e.g., Miravalles). From Latin mirari "to marvel (at)," from mira "astonishing." From Proto-Italic *smeiro- 'id.' From Proto-Indo-European *sméi̯-ro- "astonishing," but perhaps originally a collective noun meaning laughter. If it indeed meant laughter first, then the root *smei̯- meant "to laugh."
Indo-European
Romance
Portuguese mirar, Catalan mirar, French mirer, Italian mirare, Aromanian njir, Romanian mira, Sardinian mirare
Balto-Slavic
Old Church Slavonic smijati sę "smiles," Latvian smiêt "to laugh"
Hellenic
Ancient Greek φιλο-μμειδής (philo-mmeidés) "who likes to laugh"
Indo-Iranian
Sanskrit smáyate "he smiles"
Tocharian
B smiyäṃ "he smiles"