Proper noun

1. The longest river in the British Isles, that flows through Ireland into the Atlantic Ocean.
2. of origin, variant of Shanahan, anglicised from .
3. , from the surname or from the river.
   • 1896 Report of the Commission to Locate the Site of the Frontier Forts of Pennsylvania, C.M.Busch, state printer, 1896, page 283

     Captain Samuel Shannon is frequently mentioned in the public records, and he had something more than a local reputation. He must have been very popular, as the name "Shannon" as a Christian name is so common throughout the valley as to be noticeable.

4. derived from the river; first used in the USA in early 20th century, and only recently in Ireland.
   • 2005 Andrew M. Greeley, Mary G. Durkin, The Book of Love, Macmillan, 2005, ISBN 0312878389, pages 193-194

     Everything in my life is okay except I have this terrible problem with my sister Shannon. I'm spelling her name the way most people would. She spells it Sionna ever since the priest told us that's the real Irish way to spell it. It's the name of a river and a goddess. Shanny doesn't think she's a river. She's really Shannon Marie.