This is all to do with the phonaesthetics of English. I've written about it before, such as in The Cambridge Encyclopedia of the English Language, and about the general topic of sound symbolism in the Language encylopedia. There are two opposing trends:
Short vowels, plosive consonants, and monosyllables tend to be used when you want to give someone a funny or quirky (and meaningless) name - Plip, Togg, Puck ... I remember Blackadder having great fun with the name Bob once. If the sound sequence has echoes of taboo words, so much the better. Cunk inevitably brings to mind ... well, you know.
Long vowels, continuant consonants such as /l/ and /m/, and polysyllables (three or more) tend to be used when you want to give someone a gentle or romantic (and meaningless) name - Lamonian, Manderley, Ramalini ... Real names include Mariana, Valentine - and Philomena.
So it's the juxtaposition of the opposing phonaesthetic effects that provides the effect my correspondent has sensed in the name Philomena Cunk. It's a well-tried literary trick: Roald Dahl's Amanda Thripp, J K Rowling's Arabella Figg, Dr Seuss's Bartholomew Cubbins...