From Vulgar Latin illa 'id.,' from Latin illa "that one."
From Proto-Italic *olna 'id.' From Proto-Indo-European *h2ol-na- "that." From the root *h2el- "that." See also la.
Romance: Western Vulgar Latin: Asturian ella, Portuguese ela, Galician ela, Catalan ella, French ella, Italian ella; Eastern Vulgar Latin: Aromanian ea, Romanian ea
Italic: Oscan úlleís "of that," Umbrian ullu "toward that"
Indo-European: Celtic: Gaulish ollo- "beyond," Old Irish ol 'id.,' Middle Welsh ol "according to;" Balto-Slavic: Old Church Slavonic lani "last year," Czech loni 'id.'