The origin of the parish name is obscure because there have been many different spellings throughout history, including Maenor Owain, Manerowen, Manorawen and Manernawen, but the earliest recorded document is dated 1453.

[2] In 1688 John Lewis Esquire of Manernawen (sic) was appointed Commissioner for Haverfordwest under an act to collect money for a royal grant.

[5][8][9] According to the charity Parks and Gardens, the site was first created between 1650 and 1699,[10] and was recorded by Richard Fenton as belonging to his great grandfather John Lewis (see above) in the late 17th century when it was called Manarnawen.

Lewis's 1833 Topographical Dictionary of Wales notes Manorowen (or Maenor-Owain) as being a small parish[12] in the Hundred of Dewisland, with 220 inhabitants.

[14] David Jones, vicar of Llangan and an early supporter of Welsh Calvinistic Methodism, lived in Manorowen and Richard Fenton (1747-1821) is buried there.