What is the origin of the term wee hours? (Also small hours)
Wee hours the early hours of the morning after midnight. (Oxford Dictionary of English)
I also looked at Merriam, the Free Dictionary and Wiktionary. None offer a etymology of the phrase.
The Times of India claim to, but don't :
Wee hours mean the early hours of a day, or the period immediately after midnight. They are called so because the word 'wee' in present-day English means 'very small or tiny'. As these hours are the beginning of the new day they came to be referred to as the wee hours.
That comment fails to explain why being early should equate to small.
Hours have not always been consistent lengths of time. A day used to be divided into two twelve hour periods, like today, but unlike today, they were not of even lengths: the day (sunrise to sunset) was twelve hours and the night (sunset to sunrise) was twelve hours.
This meant that in the summer day hours were longer than night hours, and in the winter night hours were longer than day. In the summertime the hours after midnight (the wee/small hours) were smaller than the day hours. However this would mean that wee hours only refers to night in the summer; in the winter wee hours should refer to the daytime.