Dienstag does not necessarily mean, "day of service" as many Germans believe.
Originally, the "week" came from the Babylonians and then through the Jews to the Greeks and the Romans.
The days of the week were named after the gods of the seven ancient planets (thought to be the sun, moon, Mars, Mercury, Jupiter, Venus, and Saturn). The Germanic people learned about the planets from the Romans in about the 4th century A.D. and replaced the names with those of their corresponding German (Teutonic) gods.
The name Dienstag spread from the Lower Rhine in their dialect as Dinges, Dinsdach, and from the Middle Netherlands as Dinxendach which apparently goes back to an inscription which is Roman-Frisian from the third century A.D. named for the god Mars, Thingsus, the Thing, "protector".
Originally from Old English ping, "condition, state, meeting, court of justice"; related to pingian, "to intercede, to plead, to arrange"; Old Saxon, Old Frisian, thing, Old Norse, ping, "assembly"; Middle Dutch, dinc; Dutch, ding; Old High German, thing, ding; Middle High German, dinc, "assembly"; German Ding, "thing".
All of these words stand for the Indo-European tenkos, from the base ten-, "to extend (in space or in time)", and originally denoted "meeting at a fixed time", whence developed the meanings "affairs, things, thing". Gothic Peihs, "time"; originally meant "assembly taking place at a fixed time".
The word is a copy of the Latin Martis dies. The Germanic god is the equivalent of "heaven’s god" (himmel’s gott).
In Old High German, it was Ziu; in Old English, it was Tiw; and in Old Icelandic, it was Tyr [the name is originally related to the Greek god, Zeus, who as the god of war was changed to the equivalent Roman god, Mars.
The name of this god was also maintained in other names of the week days. For example, Alemannisch was Zistig; Middle High German, Ziestac; Old High German, Ziostag; Old English Tiwesdaeg; and Old Icelandic, Tysdagr; then Swedish, Tisdag; and English, Tuesday.
Corresponding to these names is the Bavarian, Ertag or Erchtag (Dienstag) as a word from the Gothic mission borrowed from the Greek Areos Hemera (day of Ares, meaning Mars, and Ziu). The Bavarian and Alemanisch dialect words were superseded in the 17th century by Dienstag.
Noah Webster wrote that one of the meanings for Saxon thing is "a meeting, council or convention"; thingan, thingian, "to hold a meeting, to plead, to supplicate".
He goes on to say that German ding, "a thing, a court"; dingen, "to go to law, to hire or to haggle; Dingstag, Tuesday, "thing’s day"; beding, "condition, clause".
The primary sense of the root, which is tig or thig, is "to press, to urge, to drive or to strain", and hence, its application to "courts", or "suits at law"; "a seeking of right".
We observe that Dingsdag, Dingdag, in some of the dialects signifies "Tuesday", and this from the circumstance that that day of the week was, as it still is in some states, the day of opening courts; that is, litigation day, or suitors' day, a day of striving for justice; or perhaps "combatday", the day of trial by battle.
This leads to the unfolding of another fact. Among our ancestors, Tig or Tiig, was the name of the deity of combat and war, the Teutonic Mars; that is, strife, combat deified.
This word was contracted into tiw or tu, and hence Tiwesdæg or Tuesdæg, and then Tuesday, the day consecrated to Tiig, the god of war.
It seems this is merely the day of commencing court and trial; litigation day. This Tiig, the "god of war", is strife, and this leads us to the root of thing, which is "to drive, to urge, to strive".
From Noah Webster's definition of Tuesday, we find Tiwæsdæ or Tuesdæy comes from Tig, Tiig or Tuisco, the Mars of our ancestors the deity that presided over combats, strife and litigation. Hence Tuesday is court day, assize* day; the day for combat or commencing litigation.
*Assize (uh-SIGHZ) originally was an assembly of knights and other "substantial" men. It is now considered an enactment made by a legislative assembly.
Apparently once the "fourth day" of the German week, Mittwoch, Middle High German Mit[te]woche, and before that it was Mitta-wewha in Late Old High German, which was the church (vulgar) Latin translation of "media Hebdomas".
Old High German Mittawewha has grown together from the adjective mitta (Old High German Mitti), meaning "located in the middle". The Roman Catholic Church tried to get rid of the memories of the pagan gods and goddesses by deleting formerly used Wuo-tanestag (Netherlands Woenstag; English Wednesday, and Swedish Onsdag) which were Wodansdag (Odinsdag) or tag, but now it simply means "middle-of-the-week" or Mittwoch.
"Saturday" may either be Samstag or (in some instances) Sonnabend, which means "evening before sun(day)".
Based on an Old English (Anglo-Saxon) formation, brought to Europe from England by St. Boniface (Wynfrid or Wynfrith), ca. 675-754 A.D.; during his Christian-missionary efforts to Germany.
Old English sunnan-aefen first meant the evening before Sunday, then it became sonnanaband in Old High German, and later in Middle High German sun(nen) abent. This word later referred to the whole day, not just the evening.