Is it farther or further?
1610s, "of or pertaining to an island," from Late Latin insularis, from Latin insula "island" (see isle). Metaphoric sense "narrow, prejudiced" is 1775, from notion of being cut off from intercourse with other nations, especially with reference to the situation of Great Britain. Earlier adjective in the literal sense was insulan (mid-15c.), from Latin insulanus.
insular in·su·lar (ĭn'sə-lər, ĭns'yə-)
Of or being an isolated tissue or island of tissue.