The first documentary mention of the family name Trockenbrot (Truckenbrodt, Druckenbrod - all spellings) you find in a document of a Teutonic Order subsidiary in Plauen, published in "Urkunden zur Geschichte der Deutschordens-Komturei Plauen" (= Documents for the history of the Teutonic Order subsidiary in Plauen), part II, from Dr. Walther Ludwig, Plauen 1959 (museum series number 19).
Here I try an interpretation. Please all teacher for English, Latin and history don't stone me. I'm only a math teacher and therefore a universal dilettante.
Nos Werntherus dictus de Voitisberg tenore presencium publice protestamur, quod pro salute tam nostre anime quam progenitorum nostrorum quedam bona sita in Olsnizt in vico, qui ducit in villam, que dicitur Rachsowe, que scilicet bona annis singulis duas solvunt marcas argenti, ecclesie parrochiali beati Johannis baptiste in Plawe dotavimus iure perpetuo possidenda abrenunciantes una cum nostris successoribus universis omni iure, quod in ipsis habuimus vel de cetero fuimus habituri. Que videlicet bona incolunt homines, quorum nomina hec sunt: Cunradus dictus Trockenbrot, mulier, que cognominatur Radegozin, et cuiusdam mulieris filius, que cognominatur Eckehertin. Ut hec dotacio tam racionabiliter facta rata permaneat et in perpetuum inconcussa, presentes litteras testimoniales sigilli nostri munimine fecimus roborari. Acta sunt hec anno domini M° CC° LXXXI° in domo fratrum Theutonicorum in Plawe. Huius rei testes sunt dominus Alb[ber]tus plebanus de Novo Foro, Poppo et Cuno Hunoldus in Plawe et Eckehardus ante cimiterium et dominus Siffridus prior eiusdem domus, frater Her[mann]us commendator, frater Rudolfus et alii quam plures fide digni.
We, Werner named of Vogtsberg, profess with wording of the current writing publicly, that we for our and for our ancestors salvation some estates in Oelsnitz, which are nearby the village Raschau and pay out interest two mark silver yearly, have donated to the parish church of the blessedly John the Baptist for perpetual legal property, whereby we together with all our successors renounce all rights, that we have had at it or in the future can have had. Namely these estates are occupied by vassals with following names: Konrad named Trockenbrot, a woman with the cognomen Radegozin, and the son of a woman with the cognomen Eckhartin. Therewith these so legal occured donation is valid and may be exist perpetually and unimpaired, we have let the current deed confirmed by attaching of our seal. That has occurred in the year of our Lord 1281 in the house of the Teutonic brothers in Plauen. Of this transaction are witnesses master Albrecht, parish priest of Neumark, Poppo and Kuno Hunold from Plauen and Eckhart before the cemetery and master Siegfried, prior at the very same house, brother Hermann, Komtur (=commander), brother Rudolf and very many other trustworthy persons.
Importance of the document
With the discovering of the name in the document above by Mrs. Edith Trockenbrodt the evidence has provided, that the name Trockenbrot resp. Truckenbrodt (all spellings) is older than 720 years. The latin word "dictus" is pointing to a real family name. It isn't only a cognomen or nickname. However the developement of the name must have been 2 or 3 generations ago. Here we are at the end of the 12th century in the age of the Hohenstaufen. But this is the age in Germany, where coming from the south and the west of the country family names in a narrower sense were in use for the first time. According to this the name Trockenbrot (Truckenbrodt, Druckenbrod) is one of the oldest German family names.
But must we presume the homeland of the Trockenbrot family in the Vogtland? I don't believe it, because this evidence of the name is a single monument in the Vogtland. In his book "Vogtländische Personennamen" (= names of persons in Vogtland), German-Slavonian researches for onomastics and history of settlement, volume 23, Volkmar Hellfritzsch studies the family names in the Vogtland and he uses all available sources till to the year 1530. The name Trockenbrot don't appear anymore.
If we regard, that the colonization and the settlement of the Vogtland took place in the 12th century and first of all German settlers of Eastern Franconia were coming in the former Sorbian Dobna District (Dobena District), it would appear that our Konrad or at least his ancestors belongs to these settlers from East Franconia
On this the frequency of occurrence of our family name in East Franconia (District of Coburg or Upper Franconia is the same) fits in anyway, which you can prove since the Age of Reformation. But due to a linguistic argument this theory is rather implausible. Then just as early the name can be proved on the Upper Rhine and "trocken" (= dry), well, that's an Upper German word. My considerations in detail about the developement of the family name Trockenbrot /Truckenbrodt / Druckenbrod (all spellings) you can find under the menu item surname interpretation.
Who was Werner of Vogtsberg? Did he belong to the reeves (the German word "Vogt" = reeve), which the Vogtland owes its name? To which family he belonged to and which estates had had this family? What was the relation between this family and the church of Plauen? Are there buried possibly descendants? Where the village Raschau is situated and where we have to search the estate of Konrad? Can we infer the surface of Konrad's estate from the "two mark silver - interest"? Which was the value of "two mark silver" in this age?