Ablative - is the 'grammatical case denoting removal or separation', it came to English through the Old French and Latin route, where in the Latin phrase casus ablativus we see the meaning of 'case of removal'. Here the root is Proto-Indo-European bher meaning 'to carry' and a word we still use in the sense of 'to bear children'.
Absolute - came to us from the Latin absolvere and is ultimately from Proto-Indo-European swe leu which literally means 'ourselves apart (from)'.
Accidence is derived from 'accident', itself from Proto-Indo-European ad kad 'to make fall' (which hardly sounds accidental to me!)
Accusative is clearly derived from 'accuse', which features the suffix ad used to mean 'with regard to' and the Latin causa 'a reason' which is of unknown origin.
Active came to English through the French/Latin route and is ultimately from Proto-Indo-European ag 'to drive, move'.
Adjunct is from 'adjoin', once again featuring the prefix ad 'with regard to' and the Proto-Indo-European yeug 'to join'.
Analysis comes from the Greek ana lyein, literally 'to unfasten throughout' and from Proto-Indo-European an 'upon, above' and leu 'to loosen, divide'.
Antonym is from the Greek anti 'opposite' and onym 'name' and ultimately from Proto-Indo-European anti nomm with exactly the same meaning.
Apostrophe - from the Greek apo 'off, away from' and strephein 'to turn', in turn from Proto-Indo-European apo strebh, 'to turn away'.
Article refers to anything written, with a root in Proto-Indo-European ar 'to fit together' and coming to English via articulus meaning not only 'a part' but also 'knuckle'.
Assonance features that ad suffix again, here with the Proto-Indo-European root swen to give 'with regard to sound'.
Clause shares an origin with the verb 'to close', these from Latin clausus 'to shot, close' and intriguingly from Proto-Indo-European klau meaning 'hook, peg, crooked, forked branch', all being seen in the sense of 'closing'.
Colon had me worried but only comes from the Latin word for 'part of a poem', itself from Greek kolon and used to mean 'part of a verse' but literally 'limb, member' and particularly referring to the leg but also a tree limb. These all have a root in Proto-Indo-European kel 'bent, crooked'.
Comma is the Latin for 'short phrase', itself from Greek komma 'piece which is cut off' and from the root Proto-Indo-European kop 'to beat, strike', itself also the root of 'hatchet'.
Conditional is from 'condition', itself from Latin and ultimately Proto-Indo-European deik 'to show'.
Conjugate is from the Latin coniugatus and ultimately Proto-Indo-European kom yeug 'to join together'.
Consonant is ultimately from Proto-Indo-European kom swen 'to join sound'.
Dative can be traced through Latin dativus 'pertaining to giving' to the Proto-Indo-European root do 'to give'.
Declension is from Latin declinare, also the root of 'decline', and traced back to Proto-Indo-European de 'from' and klein 'to lean'.
Decline (see above)
Definite shares a root with 'define' in de 'from' and dhigw 'pierce, fix, fasten'.
Diaeresis has two root elements, dia 'apart' and ser which means 'to seize' and shares an origin with 'heresy'.
Ellipsis has two elements, enin and leikw the Proto-Indo-European word meaning 'to leave'.
Epistrophe has two Proto-Indo-European elements epi 'near, at, against and strebh 'to wind, turn'.
Feminine comes from Proto-Indo-European dhei 'to suck' as in 'she who suckles'.
Finite shares a root with 'finish' and 'fix' in Proto-Indo-European dhigw 'to pierce, fix, fasten'.
Fricative shares an origin with 'friction' in Proto-Indo-European bhreie 'to rub, break'.
Gender shares a root with 'gene' in Proto-Indo-European gene 'to give birth'.
Hyperbaton has two Proto-Indo-European elements uper 'over' and gwa 'to go'.
Imperative also has two Proto-Indo-European elements en 'in' and pere 'to produce'.
Imperfect from the prefix im 'not, opposite of' and from the same root as 'perfect' per 'completely' and dhe to set, put'.
Interrogative comes from 'iterrogate' and Proto-Indo-European inter reg 'to stretch out in a straight line'.
Indefinite the opposite of 'definite' (see above).
Infinite the opposite of 'finite' (see above).
Intransitive is the opposite of 'transitive' (see below).
Irregular features the prefix in 'opposite of' and the Proto-Indo-European reg in 'a straight line'
Labial refers to the way a word is sounded, this from 'lip' and Proto-Indo-European leb 'to lick'.
Litotes is a Greek word meaning 'plainness, simplicity' and from the Proto-Indo-European root lei 'smily, sticky, slippery'.
Meiosis is a Greek word from the Proto-Indo-European root mei 'small'.
Metaphor again of Greek origins, where meta 'over, across' precedes Proto-Indo-European bher 'to carry' and 'bear children'.
Metre is derived from the same root as the metric measurement, this Proto-Indo-European me 'to measure'.
Neologism three Greek elements this time: neo 'new', logos 'word', and ism 'condition or quality of being'.
Nominative comes from 'nominate', itself from 'name', which is a Proto-Indo-European word nomm meaning 'name'.
Object a word which has certainly changed its meaning over time. It has two elements ob in front of, against' and the Proto-Indo-European root ye 'to throw, impel'.
Onomatopoeia still appears more Greek than English, this coming from onoma 'word, name' and the same Proto-Indo-European root as 'poet', this kwei 'to pile up, build, make'.
Oxymoron another obviously Greek word, here Proto-Indo-European ak 'be sharp, rise to a point' precedes moros 'stupid'.
Parataxis features more Greek, with para from Proto-Indo-European per 'forward, toward, near' and a Proto-Indo-European word tag 'to touch. handle' which is also the root of 'tactics'.
Parse comes from Proto-Indo-European pere 'to grant, allott'.
Particle also comes from Proto-Indo-European pere as above.
Participle shares an origin with 'participate' in Proto-Indo-European pere 'to grasp, allot' and kap 'to grasp'.
Passive comes from Latin root pati meaning 'to suffer'.
Person is of Greek origin and could share a root with the mythical Persephone in meaning 'mask'.
Semicolon while 'semi' does mean 'half', it comes from the rootsem 'imperfect' which explains why a semicolon is not half a 'colon' - if it did this wouldbe defined as 'half bent or crooked' and that would just be plain silly.
Sentence is from the past participle of 'sense', traceable to Proto-Indo-European sent 'to go'.
Simile shares an origin with 'similar' in Proto-Indo-European sem 'one, as one'.
Subject is along the lines of 'object' (see above) only here the Proto-Indo-European upo is 'under' with ye 'to throw, impel'.
Subjunctive links the prefix sub 'under' with the Proto-Indo-European root yeug 'to join'.
Subordinate another sub or 'under' with a word having the same origin as 'order', this Proto-Indo-European ar 'to fit together'.
Supine comes from the Latin supinus used figuratively to mean 'inactive, indolent' and derived from the Proto-Indo-European root sup 'under'.
Syntax is from the Greek where syn 'together' precedes tassein 'arrange'.
Transitive links the prefix trans 'across, beyond' and the Proto-Indo-European root ire 'to go'.
Vocative shares a root with 'vocal' in Proto-Indo-European wekw 'to speak'.
Vowel comes from exactly the same Proto-Indo-European root wekw 'to speak'.
Zeugma is a Greek word meaning 'that which is used for joining' literally 'a yoking' and comes from Proto-Indo-European yeug 'to join'.