Here is some of the research that I have done on the names and meaning of the gaelic words. I'm sorry if the things are a little out of order. Some of the things that were translated fully or at least partially are: Character's coven names, some of Morgan's chant, some words from spells and other gaelic words found throughout the book.
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Michelle

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giomach nm. g.v. -aich; pl. -aich, lobster

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gìomanach a hunter; from the English game

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ciara. céire, dusky, dark-grey or brown
~neimh nm. g.+e; pl.+ean, poison

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magh nm. g.v. maigh; pl.+an, field, level country, plain
mach , a mach outside (motion to "out"), Irish amach, Early Irish immach; from in and magh, a field, mach being its accusative after the prep. in, into: "into the field". Again a muigh, outside (rest), is for Early Irish immaig, in with the dat. of magh: "in the field". See

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an, ann and magh.

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sgàth nm. g.+a; v. sgàith; pl.+an, shadow, shade; dread, apprehension, sake, account
sgath va. lop off, prune, injure

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athar nm. g.v. -air, air, atmosphere, sky; also adhar
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adhar nm. See athar
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athar See athair
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athair nm. g. -ar; pl. -raichean, father

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tàth cement, join (M`F., Lh.), Irish táthaim, táth, solder or glue, Welsh todi, construc, join: *táto-, *stâto-, constitute, root sta, stand?

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mùirn joy, affection, Irish múirn, múirnín (English mavourneen, my darling), Middle Irish múirn, muirn: *morni-, root mor, mer, smer, as in muirichinn.
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beatha life, so Irish Old Irish bethu, g. bethad, Celtic stem bitât-, divided into bi-tât; See bith (i.e. bi-tu-) for root. It is usual for philologists to represent the stem of beatha as bivotât, that is bi-vo-tât-, the bi-vo- part being the same as the stem bivo of beò. While the root bi is common to both beatha and beò, the former does not contain -vo-; it is the Old Irish nom. beothu (*bi-tûs) that has set philologists wrong. Hence Gaelic and Irish beathach, animal. Irish beathadhach, dial. of beathach.
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dàn fate, destiny, Irish dán; cf. Middle Irish dán, gift, Welsh dawn, gift, talent, Latin dônum, root dó, Greek @Gdídwmi, give, Sanskrit dâ, give. dàn a poem, Irish dán, song, Old Irish dán, g. dáno, ars. *dâsnu-, root dâs, know; Greek @Gdc/nea, plans, arts, @Gdac/mon, skilful; Church Slavonic danhanh, wisdom; Sanskrit damsána, miracle (Stokes). dàn bold, Irish dána, Old Irish dáne, dána, *dâsnavo-s, from the root of dán above (Stokes).

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seòmar a chamber, Irish seómra, Middle Irish seomra; from Middle English and French chambre, Latin camera.

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braigh, hostage, pledge.

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allaidha. wild, fierce, savage

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taibhse nf. pl.+an, ghost, apparition

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an, a' the, Irish an, Old Irish in (mas. and fem.), a n- (neut.); a t- appears before vowels in the nom. masc. (an t-athair), and it is part of the article stem; a Celtic sendo-s (m.), sendâ (f.), san (n.). Sendo-s is composed of two pronominal roots, dividing into sen-do-; sen, judging by the neuter san, is a fixed neuter nom. or acc. from the Celtic root se (Indo-European sjo, beside so-, allied to Anglo-Saxon se, the, seó, now she. The -do- of sendo-s has been referred by Thurneysen and Brugmann to the pron. root to- (English tha-t, Greek @Gtó); it is suggested that to- may have degenerated into do- before it was stuck to the fixed form sen. Sen-to- could not, on any principle otherwise, whether of accentuation or what not, produce the historical forms. It is best to revert to the older etymology, and refer do- to the pronominal root appearing in the Latin fixed cases (enclitic) -dam, -dem, (qui-dam, i-dem, etc.), the Greek @G dé, @G-de (as in @Go@`/-de, this), Church Slavonic da, he. The difference, then, between Greek @Go@`/-de and Gaelic sen-do-s is this: the Greek inflects the first element ( @Go@`= so) and keeps the @G de fixed, whereas Gaelic reverses the matter by fixing the sen and inflecting the do-; otherwise the roots are the same ultimatley, and used for almost similar purposes. an in, Irish a n- (eclipsing), Old Irish i, i n-, Welsh yn, Breton en; Latin in; Greek @Ge@'n; English in, etc. Generally it appears in the longer form ann, or even as ann an; See ann. an interrogative particle, Irish an, Old Irish in; Latin an; Gothic an.

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càir a blaze, sea foam, etc.; See rather caoir. càir the gum, Irish cáir (cairib, Fol.): càir a peat moss, dry part of the peat moss (Dial.); from English carr, boggy ground, Norse kjarr, brushwood. Also càthar, q.v.

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iona, ionadh in c'iona, c'ionadh, whether: co and ionadh or iona, Early Irish inad, place. See above. The Modern Irish is ca hionad.

Resources:
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Faclair Gaidhlig - Beurla
~ There is another site I have to find the link to, I lost it! :(