Why did Coleridge adopt the pseudonym 'Satyrane'?

Easy question, no easy answer. A note in Nov 1809 The Friend explains that the name is taken from Spenser’s Faerie Queene, where ‘Sir Satyrane’ is initially a wild man, the son of a satyr, whom Una tames. He protects her against attack by other satyrs, and battles inconclusively with the lawless ‘Sansloy’. Later in the poem he chances upon Florimell's girdle, which she had lost in the process of escaping a monster. Satyrane holds a three-day tournament in which he and he and his ‘Knights of Maidenhead’ fight all-comers for the right to possess the girdle. He wins this tourney, with the assistance of Britomart. Coleridge prefaces his explanatory note with a poem, that make clear the nickname was bestowed upon Coleridge by his friends:

Tis true, IDOLOCLASTES SATYRANE
(So call him, for so mingling blame with praise
And smiles with anxious looks, his earliest friends,
Masking his birth-name, wont to character
His wild-wood fancy and impetuous zeal)

‘Idoloclastes’ means ‘breaker of Idols’. As to other possible meanings of ‘Satyrane’ as a nickname, we have only speculation. Coleridge enjoyed playing interlingual puns with his initials ‘STC’, and the ‘Sa-Ty’ portion of ‘Satyrane’ looks enough like a rubbed-down version of ‘Samuel Taylor’ to be suggestive. ‘Rane’ might glance at the Latin for ‘frog’ (a famous Gilray cartoon of 1798 had ridiculed the new poets as a toad and a frog reading a book called ‘Poems by Toad and Frog’); or it might, less decorously, take in the Greek ῥανίς, which means ‘spot’ and more particularly ‘semen, sperm’. Maybe the name means 'S. T. Cum'. Maybe not.