peninsula (n.)

late 13c., ile, from Old French ile, earlier isle, from Latin insula "island," a word of uncertain origin.

Perhaps (as the Ancients guessed) from in salo "(that which is) in the (salty) sea," from ablative of salum "the open sea," related to sal "salt" (see salt (n.)). De Vaan finds this "theoretically possible as far as the phonetics go, but being 'in the sea' is not a very precise description of what an island is; furthermore, the Indo-Europeans seem to have indicated with 'island' mainly 'river islands.' ... Since no other etymology is obvious, it may well be a loanword from an unknown language." He proposes the same lost word as the source of Old Irish inis, Welsh ynys "island" and Greek nēsos "island." The -s- was restored first in French, then in English in the late 1500s.

"of or pertaining to a peninsula; in the form of a peninsula; carried on in a peninsula," 1610s, from peninsula + -ar or from French péninsulaire (16c.). Related: Peninsularity.

The Peninsular War was the successful military operations in Spain and Portugal 1808-14 by the British and allied local forces, largely under Wellington, to drive the French from the Iberian peninsula. The Peninsular Campaign in the American Civil War was the unsuccessful attempt by the Army of the Potomac, under McClellan, in the spring and early summer of 1862 to capture Richmond, Va., by advancing up the peninsula between the Rappahannock and James rivers.