The only free and comprehensive online etymological dictionary of the Spanish language
llave f. (Noun) "key;" "wrench;" "faucet;" "switch"
13th cent. From Latin clavem, accusative of clavis "key." From Proto-Italic *klāwi- "bolt," "bar," or some simple kind of safeguarding mechanism. From *kleh2-u̯- "to close." Probably from an older root *(s)kleh2- 'id.'
Also the origin of the surnames de la Llave and Lallave.
Indo-European
Romance
Asturian llave, Portuguese chave, Galician chave, Catalan clau, French clé, Italian chiave, Aromanian cljai, Romanian cheie, Sardinian ciae
Germanic
Old High German sloz "lock," English slot
Balto-Slavic
Old Church Slavonic ključь "key," Russian ključ' 'id.,' Czech klíč "hook," Bulgarian kljúč 'id.,' Lithuanian kliū́ti "to brush against"
Hellenic
Ancient Greek κλείς (kleís) "bolt," Mycenaean ka-ra-wi- "bar," Ionic κληΐς (kleiís) 'id.'