OD, A MONOSYLLABLE.

Now, here’s a branch of the sciences that has been too long neglected. From the OED:

Od. A hypothetical force held by Baron von Reichenbach (1788-1869) to pervade all nature, manifesting itself in certain persons of sensitive temperament (streaming from their finger-tips), and exhibited especially by magnets, crystals, heat, light, and chemical action; it has been held to explain the phenomena of mesmerism and animal magnetism.

An odd name, you say? But it was chosen for impeccably logical reasons: “I will take the liberty to propose the short word Od for the force which we are engaged in examining. Every one will admit it to be desirable that a unisyllabic word beginning with a vowel should be selected… for the sake of convenient conjunction in the manifold compound words…. Instead of saying, ‘the Od derived from crystallization’, we may name this product crystallod.” (Ashburner 1850, tr. Reichenbach’s Dynamics 224). Those interested can pursue their odylic studies here. Od’s most significant appearance in literature is probably in the Seventh Book of Elizabeth Barrett Browning’s Aurora Leigh:

We think, here, you have written a good book,
And you, a woman! It was in you—yes,
I felt ’twas in you: yet I doubted half
If that od-force of German Reichenbach
Which still from female finger-tips burns blue,
Could strike out, as our masculine white heats,
To quicken a man. Forgive me. All my heart
Is quick with yours, since, just a fortnight since,
I read your book and loved it.

But it is also referred to in Avram Davidson‘s The Enquiries of Doctor Eszterhazy, a collection of stories about curious events in the Empire of Scythia-Pannonia-Transbalkania which I recommend to anyone interested in fine prose and recondite phenomena.

Update (June 2019). Upon revisiting this post (on the occasion of odylic being featured in a spelling bee), I discover that the OED updated its entry in March 2004; here’s the revised entry:

Pronunciation: Brit. /ɒd/, /əʊd/, U.S. /ɑd/, /ɔd/, /oʊd/
Forms: also with lower-case initial. […]
Origin: A borrowing from German. Etymon: German Od.
Etymology: < German Od (K. von Reichenbach 1845, in Ann. der Chem. u. Pharm. 53 216), an arbitrary formation (see quots. 1846, 1850 at sense 1).

Now hist.

1. A hypothetical force proposed by Baron Karl von Reichenbach as pervading all nature and accounting for various physical and psychological phenomena (also called odyle: see odyle n.). Frequently attributive, esp. as Od force.
The Od force was thought to manifest itself in certain persons of sensitive temperament by streaming from their fingertips, and to be exhibited especially by magnets, crystals, heat, light, and chemical action. It was held to account for the phenomena of mesmerism and animal magnetism, among other things.

1846 W. Gregory in tr. K. L. F. Reichenbach Abstr. of Res. Magn. vi. 89 The author has given to the new imponderable the name of Od, a name not possessing any meaning, but admitting of being compounded, according to the genius of the German language.
1850 J. Ashburner tr. K. L. F. Reichenbach Physico-physiol. Res. Dynamics of Magn. 224 I will take the liberty to propose the short word Od for the force which we are engaged in examining. Every one will admit it to be desirable that a unisyllabic word beginning with a vowel should be selected..for the sake of convenient conjunction in the manifold compound words.
[…]
1856 E. B. Browning Aurora Leigh vii. 295 That od-force of German Reichenbach Which still from female finger-tips burns blue.
1885 H. S. Olcott Theosophy 212 So much of light is let into the old domain of Church ‘miracles’ by mesmerism and the Od discovery.
1937 Sci. Monthly June 494/2 The claims of Baron Reichenbach, a distinguished chemist, to the discovery of another new force which he named ‘Od’, which..was found to have positive and negative qualities and to behave differently for different metals, etc.
[…]
1991 P. Heselton Elements of Earth Mysteries (BNC) 33 Von Reichenbach..published the results of numerous experiments with sensitives using techniques which enabled them to sense an energy which he called ‘the odic force’, ‘od’ or ‘odyle’.

†2. Forming the second element in various derivatives, as artemod [lunar ‘od’], biod [the ‘od’ of animal life], chymod [chemical ‘od’] , crystallod [the ‘od’ of crystallization], elod [electric ‘od’], heliod [the ‘od’ of the sun], magnetod [magnetic ‘od’], pantod [‘od’ in general], thermod [heat ‘od’], etc. Obsolete.
[Occurring only in loans and adaptations of German compounds used by Reichenbach, none of which have gained any currency outside translations of Reichenbach’s works.]

1846 W. Gregory Baron Von Reichenbach’s Abstr. Res. on Magnetism vi. 89 Thus he calls the force, abstractedly, Od; as it is found in crystals, magnets, the living body, in heat, in light, &c. Crystallod, Magnetod, Biod, Thermod, Photod, &c. Although this may answer very well in German, it is not likely that these names will be adopted in this country.
1850 J. Ashburner tr. K. L. F. Reichenbach Physico-physiol. Res. Dynamics of Magn. 224 Instead of saying, ‘the Od derived from crystallization’, we may name this product crystallod, that from animal life biod, that from heat thermod, that from electricity briefly as elod, from light photod, and so on, magnetod, chymod, heliod, artemod, tribod, and for the material world generally, pantod, &c.

I’m not convinced it was necessary to list all those derivatives, especially since they’re given in the 1850 citation, but I’m glad to know about pantod for “‘od’ in general.” Also, having seen the possible pronunciations laid out, I’m not sure how to pronounce it myself (I had been mentally saying “odd”).