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."