late 14c., "open-work metal plate affixed to an astrolabe," from Latin rete "net," a word of uncertain origin, perhaps related to Lithuanian rėtis "sieve," or perhaps a loan-word from a non-IE language. The main modern sense is anatomical, "vascular network, plexus of blood vessels" (1540s). Plural is retia. Related: Retial.
1801, "a ladies' small hand bag," originally of network, later usually of any woven material, from French réticule (18c.) "a net for the hair, a reticule," from Latin reticulum "a little net, network bag," a double diminutive of rete "net" (see rete). The telescopic attachment is so called from 1730s, from a use in French.
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Definitions of reticle from WordNet
a network of fine lines, dots, cross hairs, or wires in the focal plane of the eyepiece of an optical instrument;