The only free and comprehensive online etymological dictionary of the Spanish language
delgado (Adjective) "thin"
11th cent. From Latin delicatus "charming," "tender," "effeminate;" from an unattested verb *delicare "to charm." From de "from" (see de) and lacere "to draw," "to entice." For the etymology of lacere, from Proto-Italic *lak-i- "to draw." Of uncertain origin, though most theories place it firmly within the Indo-European family and not a loan from outside (see de Vaan (2015) for a discussion of theories).
Origin of the surnames Delgado, Delicado, and the diminutive Delgadillo, first given as nicknames to slender people.
Portuguese delgado, Galician delgado, Catalan delgat, Italian delicato
Venetic lag[sto] (?) "offered?," Oscan kellaked (?) "brought" (analyzed as *ke-le-lak-ed with a *ke- and reduplication of *lak-i)