This word is from the old Scandinavian gatlopp, which is a compound of gata, a road or street, with lopp, a course. You might not recognise the first part, but as gait it survives in English in the related sense of a manner of walking. Also, in northern England a gate is not a barrier across a road but the road itself. For example, streets in York have names such as Coppergate and Micklegate, given them by the Vikings who occupied the city before the Norman Conquest. Visitors often think that these are references to the openings in the city walls (for which the local name is actually bar, another word bequeathed by the Vikings).
Gatlopp was borrowed in the seventeenth century in the corrupted form gantlope for a type of military punishment in which a man, stripped to the waist, was forced to run between a double row of men who struck at him with sticks or knotted cords. An example turns up in Henry Fielding’s Tom Jones: “Some said, he ought to be tied neck and heels; others that he deserved to run the gantlope; and the serjeant shook his cane at him, and wished he had him under his command, swearing heartily he would make an example of him”.
Hang on a minute, you may be saying, I know that as running the gauntlet. Indeed you may. That’s the result of a folk etymology that has turned the foreign gantlope into something more familiar, in this case the old word for a fortified glove that formed part of a suit of armour. By the beginning of the nineteenth century, gantlope had vanished in favour of gauntlet, almost always in the form to run the gauntlet.
Some North Americans prefer gantlet here, which is just an earlier version of gauntlet that more closely resembles the source, the Old French gantelet.