The only free and comprehensive online etymological dictionary of the Spanish language
vacar (Verb) "to temporarily cease one's business or studies;" "to be empty"
From Latin vacare "to be free from duties;" "to be empty." Originally an adjective in Proto-Italic *wako- "empty." From Proto-Indo-European *h1u̯h2-ko- 'id.'
Indo-European
Romance
Portuguese vagar, vacar, French vaquer, Italian vacare
Italic
Latin vastus "empty"
Celtic
Old Irish fás "empty"
Germanic
Old High German wuosti "empty," Old Saxon wōsti 'id.,' Old English wōsti 'id.' (English waste)