In the book The Return of the King, Tolkien uses a word that is obscure and archaic, even for a philologist who reveled in obscure and archaic words. The context is that King Theoden and his Rohirrim are leaving Helm's Deep, en route to Edoras, and eventually Minas Tirith. Aragorn, Legolas, Gimli, and Aragorn's Dunedain brethren are not joining them.
It would be a great company; for the king was leaving only a small garrison in the Burg, and all who could be spared were riding to the weapontake at Edoras.
-The Lord of the Rings; The Return of the King, Book V, Chapter 2: "The Passing of the Grey Company"
From what I have gathered, the English word "weapontake" is based on an earlier Saxon or Norse term, "vápnatak". "Vápnatak" seems to have had several different meanings at different times. The most common usage, relatively late in the word's history, referred to an assembly of lords or tribunal; later still it came to mean the jurisdiction or district of an individual lord or group of lords. But originally, it apparently meant something else, though scholars seem to disagree as to what this meaning was. The possibilities include a ceremonial display of arms honoring a king or other royal figure along the honoree's procession route; or the act of distributing weapons to men destined for battle; or the act of collecting weapons for some reason; or an actual collection of weapons, akin to an armory.
Many people - mostly philologists and linguists prone to using dense technical jargon, often in unfamiliar dead languages - seem to be debating which meaning Tolkien had in mind when he wrote about the weapontake at Edoras. It was presumably one of the earlier definitions, related to distributing, collecting, or displaying weapons, or to a physical hoard of weaponry (located at Edoras). The later definitions - an assembly or tribunal, or an area of jurisdiction - don't make sense considering the context in which Tolkien uses the word.
It is even more difficult than one might expect to determine which definition Tolkien had in mind, because Theoden's and his company never reach Edoras- they stop at a fortress along the way and learn that Gandalf has instructed the rest of the Rohirrim to assemble at Dunharrow rather than Edoras, due to the arrival of winged Nazgul in the area of Edoras. Instead, the assembly takes place at Dunharrow, and the various events described in this part of the story fit each of the relevant definitions of "weapontake" - the King arrives and is greeted by great phalanxes of armed men; they have collected weapons from Edoras; the collected weaponry is stockpiled in the fields at Dunharrow; and before the Rohirrim ride out to Minas Tirith the next day, the weapons are distributed amongst them.
Is there a clear answer as to what Tolkien had in mind when speaking of the "weapontake"?