In reply to C Witter:
Mouse Ghyll, 1897 Mr W. Cecil Slingsby and Party
"When the first party were here, a startled mouse sprang from the grassy ledge over the leaders head, and dropped safely at the bottom of the staircase ninety feet below. May it live long enough to learn that the ghyll has been named in its honour"
O.G. Jones Rock Climbing in the English Lake District