I had not realised that T.S. Eliot was a Sherlock Holmes fan until I thought to look up the word grimpen, which occurs in ‘East Coker’, in the Four Quartets: ‘On the edge of a grimpen, where is no secure foothold.’
We take grimpen to mean ‘a bog’. The OED undogmatically gives the meaning as ‘marshy area’, and the etymology as ‘uncertain’. This is no surprise since the word, it appears, was made up by Sir Arthur Conan Doyle for The Hound of the Baskervilles.
Watson is on Dartmoor with Stapleton the naturalist. ‘“That is the great Grimpen Mire,” said he. “A false step yonder means death to man or beast.”’ Conan Doyle usually attaches the epithet ‘great’ to the Grimpen Mire in a Homeric manner. It must be noted that mire is the part of the name that signifies ‘a bog’. Grimpen is also the name of the local hamlet, and is doubtless derived from Grimspound on Dartmoor, where there are the remains of a prehistoric village.
Grim occurs in many English place-names such as Grims Dyke, Wiltshire, or Grims Ditch, Hertfordshire, where the reference is to the Devil. Grimsby is claimed for a man called Grim. In all cases the name goes back to Grim or Grimr, a name for the god Othinn. His name means ‘fierce’, ‘cruel’, ‘savage’, as the English adjective meant at the time Beowulf was written.
Eliot made another daring raid on Sherlock Holmes for Murder in the Cathedral, in the dialogue between Thomas Becket and the Second Tempter. ‘Thomas: Who shall have it? Tempter: He who will come. Thomas: What shall be the month? Tempter: The last from the first.