Webster's Revised Unabridged Dictionary · 1913

January

January , noun

[Latin Januarius, from Janus an old Latin deity, the god of the sun and the year, to whom the month of January was sacred; compare janua a door, Sanskrit to go.]

The first month of the year, containing thirty-one days.

Before the adoption of New Style, the commencement of the year was usually reckoned from March 25.