Wednesday named after Mercury
Wednesday is the day of the week between Tuesday and Thursday.  According to international standard ISO 8601, it is the third day of the week. In countries which have Friday as their holiday, Wednesday is the fifth day of the week. In countries which use the Sunday-first convention, and in both the Islamic and Jewish calendars, Wednesday is the fourth day of the week.
In English, the name is derived from Old English Wōdnesdæg and Middle English Wednesdei, 'day of Woden', reflecting the religion practiced by the Anglo-Saxons, the English equivalent to the Norse god Odin. In many Romance languages, such as the French mercredi, Spanish miércoles or Italian mercoledì, the day's name is a calque of Latin dies Mercurii 'day of Mercury'.
Wednesday is in the middle of the common Western five-day workweek that starts on Monday and finishes on Friday.Etymology
See Names of the days of the week for more on naming conventions.The name Wednesday continues Middle English Wednesdei. Old English still had wōdnesdæg, which would be continued as *Wodnesday  (but Old Frisian has an attested wednesdei). By the early 13th century, the i-mutated form was introduced unetymologically.The name is a calque of the Latin dies Mercurii 'day of Mercury', reflecting the fact that the Germanic god Woden (Wodanaz or Odin) during the Roman era was interpreted as "Germanic Mercury".
The Latin name dates to the late 2nd or early 3rd century. It is a calque of Greek ἡμέρα Ἕρμου (heméra Hérmou), a term first attested, together with the system of naming the seven weekdays after the seven classical planets, in the Anthologiarum by Vettius Valens (c. AD 170).
The Latin name is reflected directly in the weekday name in most modern Romance languages: mércuris (Sardinian), mercredi (French), mercoledì (Italian), miércoles (Spanish), miercuri (Romanian), dimecres (Catalan), marcuri or mercuri (Corsican), mèrcore (Venetian). In Welsh it is Dydd Mercher, meaning 'Mercury's Day'.
The Dutch name for the day, woensdag, has the same etymology as English Wednesday; it comes from Middle Dutch wodenesdag, woedensdag ('Wodan's day').
The German name for the day, Mittwoch (literally: 'mid-week'), replaced the former name Wodenstag ('Wodan's day') in the 10th century. (Similarly, the Yiddish word for Wednesday is מיטוואך (mitvokh), meaning and sounding a lot like the German word it came from.)
Most Slavic languages follow this pattern and use derivations of 'the middle' (Belarusian серада serada, Bulgarian сряда sryada, Croatian srijeda, Czech středa, Macedonian среда sreda, Polish środa, Russian среда sredá, Serbian среда sreda or cриједа srijeda, Slovak streda, Slovene sreda, Ukrainian середа sereda). 
The Finnish name is keskiviikko ('middle of the week'), as is the Icelandic name: miðvikudagur, and the Faroese name: mikudagur ('mid-week day').  Some dialects of Faroese have ónsdagur, though, which shares etymology with Wednesday. Danish, Norwegian, Swedish onsdag, (Ons-dag meaning Odens dag 'Odin's day').
In Japanese, the word for Wednesday is 水曜日 (sui youbi) meaning 'water day' and is associated with 水星 (suisei): Mercury (the planet), literally meaning 'water star'. Similarly, in Korean the word for Wednesday is 수요일; su yo il, also meaning 'water day'.
In most of the languages of India, the word for Wednesday is Budhavāra — vāra meaning 'day' and Budha being the planet Mercury.
In Armenian (Չորեքշաբթի chorekshabti), Georgian (ოთხშაბათი otkhshabati), Turkish (çarşamba), and Tajik (chorshanbiyev) languages the word literally means 'four (days) from Saturday' originating from Persian (چهارشنبه cheharshanbeh).
Portuguese uses the word quarta-feira, meaning 'fourth day', while in Greek the word is Tetarti (Τετάρτη) meaning simply 'fourth'. Similarly, Arabic أربعاء means 'fourth', Hebrew רביעי means 'fourth', and Persian چهارشنبه means 'fourth day'. Yet the name for the day in Estonian kolmapäev, Lithuanian trečiadienis, and Latvian trešdiena means 'third day' while in Mandarin Chinese 星期三 (xīngqīsān), means 'day three', as Sunday is unnumbered.Astrology
The astrological sign of the planet Mercury, ☿, represents Wednesday—dies Mercurii to the Romans, it had similar names in Latin-derived languages, such as the Italian mercoledì (dì means 'day'), the French mercredi, and the Spanish miércoles. In English, this became "Woden's Day", since the Roman god Mercury was identified by Woden in Northern Europe and it is especially aligned by the astrological signs of Gemini and Virgo.
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