picket n.

"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"Formerly the chief weapon of a large part of the infantry; in the 18th c. superseded by the bayonet" [OED]; hence old expressions such as pass through pikes "come through difficulties, run the gauntlet;" push of pikes "close-quarters combat."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.