Who coined the word "permittivity"? It appears that first usage was in 1887. Please cite your source.
Oliver Heaviside "On the Self Inductance of Wires" Philosophical Magazine Series 5, volume 24, issue 146, 1887.
No it was known well before 1887. Faraday was looking for a word to indicate a material through which an electrical field would penetrate. He asked William Whewell - a polymath at Cambridge (UK), who suggested dielectric (considering dia-electric a bit clumsy): "As to the name for the antithetical classes of bodies, I consider thus. I suppose you called one class dimagnetic from analogy with dielectric. I think you ought to have said diamagnetic; for the bodies through (dia) which electricity goes would have been called diaelectric, but that vowels in such cases coalesce. I think you may keep diamagnetic for this class, and give to the opposite class a name implying that they rank along with magnetic bodies. I propose paramagnetic. (Whewell's emphasis)"
J. Daintith (1994). Biographical Encyclopedia of Scientists. CRC Press. p. 943. ISBN 0-7503-0287-9.
Jump up ^ James, Frank A.J.L., editor. The Correspondence of Michael Faraday, Volume 3, 1841–1848, "Letter 1798, William Whewell to Faraday, p. 442.". The Institution of Electrical Engineers, London, United Kingdom, 1996. ISBN 0-86341-250-5