1620s, an old measure of land in Holland (hence also in South Africa and colonial New York and New Jersey), roughly two acres but sometimes less, probably identical with Dutch morgen "morning" (see morn) and meaning "the amount of land one man can plow in a morning."

"the first part of the day, the morning," late 14c., contracted from Middle English morwen, morghen, from Old English (Mercian) margen (dative marne), earlier morgen (dative morgne) "morning, forenoon, sunrise," from Proto-Germanic *murgana- "morning" (source also of Old Saxon morgan, Old Frisian morgen, Middle Dutch morghen, Dutch morgen, Old High German morgan, German Morgen, Gothic maurgins), from PIE *merk-, perhaps from root *mer- "to blink, twinkle" (source of Lithuanian mirgėti "to blink"). By late 19c. relegated to poetry.