Notebooks 1:303 is a bit of Latin:
ingenium ei esse oppido magnum sed contumacius quam ut arte regi posset; dictionem ingenio parem, animosam, et imamoenam tragice que ferulem.Kathleen Coburn translates this, although she doesn't quite get it right: ‘[that] town has a great genius, but more insolent than could be commanded by art—a style equal to genius, proud, gloomy, and tragically dangerous.’ In fact, for reasons that will become clear, oppidum can't mean town here, but must be a way of saying something like ‘edifice, construction’, or more likely ‘assemblage, collection’. I offer my translation of the Latin at the end of this blogpost.
Coburn can't identify where it's from. In fact it is Famiano Strada, a seventeenth-century Roman Jesuit, and he's talking not about any city but about the poet Lucan and his epic poem of Roman civil war the Pharsalia. The Latin is originally from Strada's Eloquentia bipartita (1655), [p.368 in fact] but that's not where Coleridge came across it. We can be sure of this because Strada actually wrote not ‘animosam, et imamoenam’ but ‘animosam, peracutam, eruditam et imamoenam’. The specific phrasing that Coleridge wrote down in his Notebook evidently derives from the Critical Review for 1797 (p.462) and a review of The Rural Lyre; a Volume of Poems (1796) by Ann Yearsley, a former Bristol milk-maid who had found fame as a poet. This is how the review opens:
This is interesting for a couple of reasons. One is that it means we can be sure Coleridge read this volume of the Critical Review. Another is that Coleridge perhaps knew, and certainly knew of, fellow-Bristolian Yearsley: her poems were quite famous. at least for a while; Coleridge's friend the Bristol publisher Joseph Cottle gave Yearsley money to save her from bankruptcy, and several decades after her death (in 1831) Robert Southey wrote her biography.
But my hunch is that Coleridge pulled this Latin out of the journal he was reading less because of what it says about Yearsley and more because it struck him as a description of his own poetry. As he notes in the opening chapter of the Biographia, critics had accused his first book Poems on Various Subjects (1796) of ‘obscurity’ and ‘a general turgidness of diction’. Strada could have been talking about STC's own work: ‘a collection of a more inflexible temper than can be managed by its artistry, where the style matches its author's genius: spirited, but tragically obscure and stiff.’