"small;" (masc.) "boy," "child;" (fem.) "girl"
12th cent. Perhaps from Latin ciccus "nothing," earlier "something worthless," but originally "the thin membrane surrounding the grains of a pomegranate." Presumably borrowed from an unattested Ancient Greek word *κίκκος (kíkkos) "shell of a pomegranate," hypothesized by Beekes (2008) on the basis of the Latin word and possible Greek derivatives κίκκαβος (kíkkabos) "small coin in the Underworld," κικκάβι(ο)ν (kikkábi(o)n) "nothing," and κικαῖος (kikaîos), a word of obscure meaning.
Ultimately of unknown origin.
Also the origin of the surname Chico.
Western Vulgar Latin: Asturian chico, Aragonese chicot, Catalan xic, French chiquet, Italian cica
The sense of "small" was first and then was extended to children. The change from c-
may have been reinforced by Basque, cf. txiki
"small," "few," from earlier tiki
. Also note 18th cent. colloquialism chicho
"small child (who has begun to speak)," from *cic(c)us
via double-palatalization distortion found in children's speech (compare niño