This article is from the Calendars FAQ, by Claus Tondering claus@tondering.dk with numerous contributions by others.
A lot of languages, including English, use month names based on Latin.
Their meaning is listed below. However, some languages (Czech and
Polish, for example) use quite different names.
January Latin: Januarius. Named after the god Janus.
February Latin: Februarius. Named after Februa, the purification
festival.
March Latin: Martius. Named after the god Mars.
April Latin: Aprilis. Named either after the goddess Aphrodite or
the Latin word "aperire", to open.
May Latin: Maius. Probably named after the goddess Maia.
June Latin: Junius. Probably named after the goddess Juno.
July Latin: Julius. Named after Julius Caesar in 44 BC. Prior
to that time its name was Quintilis from the word
"quintus", fifth, because it was the 5th month in the old
Roman calendar.
August Latin: Augustus. Named after emperor Augustus in 8
BC. Prior to that time the name was Sextilis from the
word "sextus", sixth, because it was the 6th month in the
old Roman calendar.
September Latin: September. From the word "septem", seven, because
it was the 7th month in the old Roman calendar.
October Latin: October. From the word "octo", eight, because it
was the 8th month in the old Roman calendar.
November Latin: November. From the word "novem", nine, because it
was the 9th month in the old Roman calendar.
December Latin: December. From the word "decem", ten, because it
was the 10th month in the old Roman calendar.
 
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