pike (n.4) Look up pike at Dictionary.com
"pick used in digging," Middle English pik, pyk, collateral (long-vowel) form of pic (source of pick (n.1)), from Old English piic "pointed object, pickaxe," perhaps from a Celtic source (compare Gaelic pic "pickaxe," Irish pice "pike, pitchfork"). Extended early 13c. to "pointed tip" of anything. Pike, pick, and pitch formerly were used indifferently in English. Pike position in diving, gymnastics, etc., attested from 1928, perhaps on the notion of "tapering to a point."
pike (n.1) Look up pike at Dictionary.com
"highway," 1812 shortening of turnpike.
pike (n.2) Look up pike at Dictionary.com
"weapon with a long shaft and a pointed metal head," 1510s, from Middle French pique "a spear; pikeman," from piquer "to pick, puncture, pierce," from Old French pic "sharp point or spike," a general continental term (Spanish pica, Italian picca, Provençal piqua), perhaps ultimately from a Germanic [Barnhart] or Celtic source (see pike (n.4)). Alternative explanation traces the Old French word (via Vulgar Latin *piccare "to prick, pierce") to Latin picus "woodpecker." "Formerly the chief weapon of a large part of the infantry; in the 18th c. superseded by the bayonet" [OED]; hence old expressions such as pass through pikes "come through difficulties, run the gauntlet;" push of pikes "close-quarters combat." German Pike, Dutch piek, Danish pik, etc. are from French pique.
pike (n.3) Look up pike at Dictionary.com
"voracious freshwater fish," early 14c., probably short for pike-fish, a special use of pike (n.2) in reference to the fish's long, pointed jaw, and in part from French brochet "pike" (fish), from broche "a roasting spit."