Pike
Middle English: from pike2 (because of the fish's pointed jaw).
wiktionary
From Middle English pyke, pyk, pik, pike(“pike; sharp point, iron tip of a staff or spear, pointed toe of an item of footwear; sharp tool; mountain, peak”), from Old English pīc(“pointed object, pick axe”), [1] and Middle French pique(“long thrusting weapon”), from Old French pic(“sharp point, spike”); [2] both ultimately from Proto-Germanic *pīkaz, *pīkō(“sharp point, pike, peak”), related to pick with a narrower meaning.
The word is cognate with Middle Dutch pecke, peke, picke (modern Dutch piek), German Pike, Norwegian pik, and possibly Old Irish pīk. It is a doublet of pique.
The diving or gymnastics position is probably from tapered appearance of the body when the position is executed. [1]
The carnivorous freshwater fish is probably derived from the “sharp point, spike” senses, [3] due to the fish’s pointed jaws. [4]
The verb sense “to quit or back out of a promise” may be from the sense of taking up pilgrim's staff or pike and leaving on a pilgrimage; [4] and compare Middle English pī̆ken(“to go, remove oneself”) and Old Danish pikke af(“to go away”). [5]
Clipping of turnpike(“a toll road, especially a toll expressway; a spiked barrier across a road, originally used to block access to the road until toll had been paid”).
Noun sense 2 (“gypsy, itinerant tramp, or traveller”) and verb sense 2 (“to depart, travel, especially to flee, run away”) may refer to someone frequently using turnpikes, or may be derived from Middle English pī̆ken(“to go, remove oneself”). [5]
etymonline
pike (n.1)
"weapon with a long shaft and a pointed metal head," 1510s, from 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.2)). An alternative explanation traces the Old French word (via Vulgar Latin *piccare "to prick, pierce") to Latin picus "woodpecker." No doubt, too, there is influence from pike (n.1), which by 1200 had a sense of "spiked staff."
"Formerly the chief weapon of a large part of the infantry; in the 18th c. superseded by the bayonet" [OED]; hence old expressions such as pass through pikes "come through difficulties, run the gauntlet;" push of pikes "close-quarters combat."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.2)
early 13c., pik, pyk, "pointed tip or spike on a staff, pole, weapon, etc.," collateral (long-vowel) form of pic (source of pick (n.1)), from Old English piic "pointed object, pickaxe," which is perhaps from a Celtic source (compare Gaelic pic "pickaxe," Irish pice "pike, pitchfork"). The word probably has been influenced by, or is partly from, Old French pic "sharp point or spike," itself perhaps from Germanic (see pike (n.1)), Old Norse pic, and Middle Dutch picke, pecke. Pike, pick (n.1), and pitch (n.1) formerly were used indifferently in English.
From c. 1400 as "a sharp, pointed mountain or summit." The pike position in diving, gymnastics, etc., is attested by 1928, perhaps on the notion of "tapering to a point."
pike (n.3)
"type of long, slender, voracious freshwater fish," early 14c., pik (mid-12c. in place names), 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." In Middle English, proverbial for health and vigor.
pike (n.4)
"highway," 1812 shortening of turnpike.
