Bryan,
Stuart Marshal, author of "Walking the Wainwrights", has sent me the following comments on obscure Wainwright fell names. He is happy to follow this up with you direct and I will send you his e-mail address.
The best source for the derivation/meaning of Lake District place-names is Diana Whaley's 'Dictionary' (English Place-Name Society, Nottingham 2006). This valuable book distills all the material in the EPNS county volumes – three for Cumberland and two for Westmorland. The author does sometimes seem to strain a bit to find something to say about a hill name, but that is understandable.
After consulting these sources, I believe that the names of the 'Wainwrights' in the following list are hard to explain. A few that have some sort of explanation are included in the list, but the rest, ignoring feeble or far-out suggestions, seem to have no accepted etymology.
Ard Crags 'Ard' may possibly come from a Celtic word meaning height or hill
Beda Fell Unexplained
Bakestall Unexplained
Bonscale Pike The 'bon' element is elusive, but may be derived from bondi: freeholder.
Brim Fell 'Brim' could describe the steep edge of the hill, but most hills are like that!
Carl Side 'Carl' may come from an ON word meaning old man (cf. Carling: old woman)
Dollywaggon Pike "Defies explanation" according to Whaley, though somewhere else I've seen a
derivation from the name for a wheeled sled – but why?
Froswick Obscure, especially as 'wick' is surprising as an element of a hill name
Great Borne 'Borne' may derive from a parish boundary (or a stone marker) near by
Grey Friar The possible explanations put forward in Whaley are very fanciful
Helvellyn Unexplained (the lack of a good etymology for such a venerable hill is surprising)
Hen Comb "Ridge frequented by (female) wild birds" (Whaley)
High Tove 'Tove' may be from a dialect word meaning tuft (or tussock?). In one source (1805) the name is given as 'High Tooves'.
Maiden Moor Unexplained
Pavey Ark Uncertain – 'Pavia's shieling' is one ingenious suggestion
Pike of Blisco Unexplained
Rest Dodd Whaley's suggestion that a resting place is the source seems inadequate
Sallows Possibly from the OE name for willows – though they don't grow there now
Skiddaw The full entry in Whaley should be consulted, but to me it lacks conviction
Sour Howes 'Poor, wet' plus 'bumpy hill top' is the straightforward explanation
Thunacar Knott Obscure, but an ON personal (nick)name has been suggested as the source
Wansfell 'Wans' is obscure but may come from a personal name, or an ON plant name
Whiteless Pike The 'less' element is obscure
Yoke Whaley finds it plausible that the name refers to the short bowed ridge which connects Yoke to Ill Bell (I don't find that convincing but I have no better solution)