The only free and comprehensive online etymological dictionary of the Spanish language
lleno (Adjective) "full"

12th cent. From Latin plenus 'id.' From a fossilized verb in Proto-Italic *plē- "to fill." From *pleh1- 'id.'

Romance: Western Vulgar Latin: Asturian llenu, Portuguese cheio, Galician cheo, Catalan ple, French plein, Italian pieno; Eastern Vulgar Latin: Aromanian plin, Romanian plin; Sardinian: pienu

Italic: Umbrian pleno "fullness"

Indo-European: Celtic: Gaulish Urido-lanos (name) "full of justice," Old Irish lán "full," Middle Welsh llawn 'id.,' Old Breton -lon 'id.,' Cornish luen 'id.;' Germanic: Gothic fulls "full," Old Norse fullr 'id.,' Old High German fol 'id.,' Old Saxon full 'id.,' English full; Balto-Slavic: Old Church Slavonic plъnъ "full," Russian pólnyj 'id.,' Czech plný 'id.,' Polish peɫny 'id.,' Bulgarian pắlen 'id.,' Lithuanian pìlnas 'id.,' Latvian pil̃ns 'id.;' Hellenic: Ancient Greek πλήρης (pléres) "full;" Armenian: lnow- "to fill;" Indo-Iranian: Sanskrit pr̥ṇā́ti "to fill," Old Avestan pərənā "you fulfill"