@grenadier corporal,
Many thanks – further info below extracted from Enrico Acerbi's excellent "The Austrian Imperial-Royal Army (Kaiserliche-Königliche Heer) 1805 – 1809: A Dictionary of K.K. Austrian Regimental Positions and Ranks" at link
Feldwebel
Feld=Field Webel=(Wiebel) [10] administrative servant. Was the first NCO of the company in not mounted units and the supervisory for the inner duties in a company. This word comes from the Landsknechte period. Stood in the middle of the battlefield near the Banderuole (Banderols, ancient patrols equivalent of companies – German Fähnlein) in order to transmit the Landsknechte Hauptmann orders, on what the Gemeine had or not had to perform; also administered fees. Near the Feldwebel stood the Stellvertreter der Hauptleute (deputies of higher officers), since then called Lieutenants.
In more modern periods the Feldwebel overlooked at the company organization, made the company's reports, administered the payments for the soldiers, and so on. In German armies the vice-Feldwebel were named Sergeanten or Unteroffizieren and often carried the bataillon's flags. This qualified the rank as similar to a current Sergeant-major. The Feldwebel were selected without taking into consideration seniority, only after the promotion from sergeants and non-commissioned officers. Practically he did, in the company, what the Adjutanten did in the regiment.
Since 1769 they were transferred in the Lesser Prima-Plana lists and so they acquired the right to voluntarily dismiss themselves from service, having a not mandatory Military Duty time.
In the Austrian army, as for the two etymologies, there were Feldwebel and Rechnung-Feldwebel (payments).
Austrian army Equivalents:
Light troops (Jäger) =Oberjäger
Cavalry =Wachtmeister
Artillery =Feuerwerker
Feldwebel in the Napoleonic times as well as before and after, is a rank, he is the highest ranking NCO within a company and there is always only one Feldwebel per company in peacetime. His equivalent in the French army is sergent-major. While in peacetime there was one Feldwebel per company during the wartime, after 1805, each company had one more Feldwebel (a more Zimmermann too). Since November 1, 1849, the second Feldwebel became mandatory also in peacetime, from that time assuming distinctive administrative tasks.
Fourierschütz
Obviously the important tasks assigned to a Fourier needed his personal body-guards. These were the Fourierschützen, in the Landsknechts armies called also Trabanten or Leibschützen. Sometimes they were present in stated amounts (i.e. 12 for the Obrist, 6 for the Hauptmann). During the time evolution, the necessity to act as body-guard began to be less important, so they became the real Fourier's helpers. Under the Prince Eugene rule their number was fixed in four per Company Commander (or Staff officer). There were also other service personnel in the Austrian army called Nachwuchs or Novizen, at that time. On 1726 the number of the Fourierschützen was lowered to two per Company Commander (or Staff officer). On 1767 there was only one Fourierschütz attached as a Fourier's aide. He had to help to find the quarters and expecially the officer's accomodations and services.
On 1771, during the peacetime, every officer and Fahnen-Cadett had one Gemeine at their service. These new Fourierschützen were called Privatdiener. They were free from the common military duties, in order to serve the officers. On 1779 also the Auditoren, the Rechnungsführern and the Adjutanten had their Privatdiener. On 1801 all the Staff officers, and the companies commanders (that is also the Capitain-Lieutenants) had a Fourierschütz at their service, while the other higher officers (Regiments-Caplanen, -Ärzte and Auditoren too) had their personal Privatdiener, who had the same wage and uniform [11] as the Gemeine. These soldier were often taken from the invalids or the partialy fit men. (from 1808 they were chosen among the half-invalids of the regiment). The Privatdiener on 1853 received the name of Offiziersdiener and were attached only to Higher and Staff officers.
Adjutant
1- Wachtmeister Lieutenant or Regiments-Adjutant
The first time this charge was observed was in a Verpflegs-Ordonnanz of 1648. He was the "factotum" of the regiment, the right arm of the Obrist Commandant, kept the regiment's lists, the services distribution, diffused the Chief's orders and, in battle, directly defended the Obrist. Dressed like an officer and mounted, he had the rank of the upper Senior Feldwebel. From 1769 his name changed to Regiments-Adjutant.
On 1803 they reached the rank of Fähnriche and, on 1807, they had to use a sabre only in face of the enemy and for personal defence. During the XIX century they gradually acquired the mansions of the Auditore and those of the Secretären; from 1861 they received also a governative (Ärarisch) horse for the duty.
2- Bataillons-Adjutant
This Charge was established on 1769, for the kombinierte-Grenadiers-bataillone. They served in the grenadier battalions in the same way the Regiments-Adjutant served the regiment. During the first Revolutionary wars period (1792-1801) they appeared also in the regular battalions Staffs. This became official (also for the peacetime) after 1803.