The City of London, in its early days, was well supplied with water, not only by the wells dug near houses, or by the public springs, some of which still exist, as Aldgate Pump, &c., and the River Thames; but, when its borders increased, the Walbrook was utilized, as well as the Fleet, and, later on, the Tye-bourne, or twin brook, which fell into the Thames at Westminster. In the course of time these rivulets became polluted, land was valuable; they were covered over, and are now sewers. The course of the Fleet being clearly traceable in the depression of Farringdon Street, and the windings of the Tye-bourne in the somewhat tortuous Marylebone Lane (so called from the Chapel of St. Mary, which was on the banks of "le bourne," or the brook[1]). Its further course is kept in our memory by Brook Street, Hanover Square.
The name of this little river has exercised many minds, and has been the cause of spoiling much good paper. My own opinion, backed by many antiquaries, is that a _Fleet_ means a brook, or tributary to a larger river, which is so wide, and deep, at its junction with the greater stream as to be navigable for the small craft then in use, for some little distance. Thus, we have the names on the Thames of Purfleet, Northfleet, and Southfleet, and the same obtains in other places. Its derivation seems to be Saxon--at least, for our language. Thus, in Bosworth's "Dictionary of the Anglo-Saxon Language," we find, "Flede-Fledu: part. _Flooded_; _overflowed_: tumidus[2]: Tiber fledu wearð[3]--the Tiber was flooded (Ors. 4. 7)."
Again, the same author gives: "Fleot (_Plat_ fleet, m. _a small river_; _Ger._ flethe. f. _a channel_). _A place where vessels float_, _a bay_, _gulf_, _an arm of the sea_, _the mouth of a river_, _a river_; hence the names of places, as _Northfleet_, _Southfleet_, _Kent_; and in London, _Fleet ditch_; _sinus_.[4] Soes Fleot, _a bay of the sea_.[5] _Bd._ 1. 34."
Another great Anglo-Saxon scholar--Professor Skeat, in "An Etymological Dictionary of the English Language": "Fleet, a creek, bay. In the names _North-fleet_, _Fleet_ Street, &c. Fleet Street was so named from the Fleet Ditch; and _fleet_ was given to any shallow creek, or stream, or channel of water. See Halliwell. M.E. _fleet_ (Promptorium Parvulorum, &c., p. 166). A.S. _fleót_, a bay of the sea, as in Soes Fleot, bay of the sea. Ælfred's tr. of Beda, i. 34.[5] Afterwards applied to any channel or stream, especially if shallow. The original sense was 'a place where vessels float,' and the derivation is from the old verb _fleet_, to float, &c."