Meaning

noun an eating disorder, frequent in children, in which non-nutritional objects are eaten persistently

noun a linear unit (1/6 inch) used in printing

noun magpies

originFrom Medieval Latin pica (“pica: a service book”), possibly from Latin pīca (“magpie”) after the piebald appearance of the typeset page (cf. pie (“disordered type”)). The relation to the printer's measure is unclear, as no edition of the text in pica type is known. The French pica derives from English rather than vice versa.

Etymology from Wiktionary, CC BY-SA 3.0