'Asra' was Coleridge's private name for Sara Hutchinson (1775-1835). There she is, in the image above (from Richard Holmes's Coleridge: Darker Reflections, 1998); on the left Wordsworth's own silhouette of her, and on the right a figure from Ciro Ferri's 'The Marriage of Boas and Ruth', that Coleridge saw in Bolton Abbey in 1810, and which he claimed reminded him of Sara.
She was the younger sister of Mary Hutchinson, who married Wordsworth in 1802; Sara lived with her sister and new brother-in-law for many years. By most accounts she was an attractive woman, lively, diminutive and curvaceous; although some disliked her (some members of the Wordsworth circle, having failed to fall under her spell, called her large-chinned and -nosed, dumpy and wearing. Harsh!). Coleridge, however, fell deeply in love with her after meeting her in 1799. Nothing came of this. Sara seems to have been fond of Coleridge, and was in many ways a good friend to him, going so far as to act as amanuensis during the long composition of The Friend, 1809-10. But she doesn't seem to have desired him physically, or loved him, certainly not with the intensity that he desired and loved her; and when we factor-in her respectability (agreed upon by all), and already-married Coleridge's own deeply-held religious scruples where adultery and divorce were concerned, we can be pretty sure the 'affair' was unconsummated. But that doesn't negate the intensity of Coleridge's despairing longing; quite the reverse, of course. His notebooks and many of his poems return obsessively to 'Asra', to his love and desire and despair about her. Some of his finest poems, indeed, were inspired by her, although, as Richard Holmes notes in his thumbnail portrait (from his Penguin Coleridge: Selected Poetry, 1996):
... she was not a conventionally romantic, dreamy Muse. She was cheerful and outgoing, a small energetic figure with a mass of auburn hair, quick and neat in the house, and daring and eager on country walks. Many of Coleridge's tenderest memories of her are in the snug, firelit farmhouse kitchen.So why 'Asra'? As anagrams go, it's a pretty flimsy code for 'Sara'; although since Coleridge's wife was also called Sara it at least helps critics and biographers to distinguish between them. The impression Coleridge gives in his notebooks where his wife is concerned is one of sexual frigidity (of course, we're only getting his side of the picture): in one entry he laments that when the two of them get naked together 'all [is] as cold & calm as a deep Frost' adding that she 'is uncommonly cold in her feelings of animal Love' [Notebooks 1:979]. By contrast, 'Asra' is characterised in his notes in terms of warmth: firelight, warm climates, exoticism.
The first intimation of the 'Asra' nickname is in a present Coleridge gave Sara Hutchinson for Christmas 1800: an edition of Anna Seward's Original Sonnets (1799), which he inscribed: 'to Asahara, the Moorish Maid'. Presumably this records some private joke that the auburn-haired Sara had an oriental look about her: I suppose that 'Asahara' filters the Arabic 'Ashura' or maybe the Assyrian deity 'Ashur' via the letters of 'Sara'. Conceivably it also picks up on the female-personified 'orient' IMAGINATION which Seward writes about, and who adorns the frontispiece to the Original Sonnets. 'Come, bright IMAGINATION come relume/Thy orient lamp' says the legend under the picture, quoting from Seward's first sonnet. Did Coleridge fancy a resemblance between Sara Hutchinson and this figure? Did he make a joke of it with her, and so orientalise her name? Did he secretly yearn that she would come and *coughs* relume his orient lamp? I'm guessing: yes. Yes he did.
Coleridge's physical desire for Sara was inextricably tangled not only with its own impossibility, but with his deep reservoirs of self-disgust. This in turn leads me to believe that Coleridge had in mind ἀσαρα ('ἀσ'ρα'): a shortened form of the Ancient Greek ἀσαραός, sometimes spelled ἀσηραός, which means (to quote Liddell and Scott) ‘causing nausea’, or ‘feeling disgust or disdainful of a woman’. L&S cite Sappho 78 for this latter meaning. Perhaps this seemingly simple anagram encodes physical disgust. He was presumably also aware that the Ancient Greek for the vagina (what L&S primly call 'pudenda muliebria') is a 'sara' word: σάραβος.