The only free and comprehensive online etymological dictionary of the Spanish language
bajo (Adjective; Adverb) "short," "low"
13th cent. From Latin bassus "base;" "fat." Borrowed from Ancient Greek βαρύς (barys) "heavy," "low." From Proto-Indo-European *gwr̥h2-u- 'id.' From *gwreh2- "to be heavy" (whence grave).
Indo-European
Romance
Asturian baxu, Portuguese baixo, Galician baixo, Catalan baix, French bas, Italian basso
Italic
Latin gravis "heavy," Oscan bravús 'id.'
Germanic
Gothic kaurjos "heavy"
Indo-Iranian
Sanskrit gurú- "heavy"