Daniel T. Sheehan was a friend of Joyce’s from university days. He was credited by the author with the invention of a word (aquacity) which Joyce wove into his fiction.
Stanislaus Joyce introduces us to Sheehan and his new word:
A medical student by name Sheehan (an oval-faced, under-shod fellow with a small curly head like an Assyrian king) should be given a civil list pension for a word with which he has enriched the vocabulary — Aquacity. He applied it to various statements and platitudes [...] James Joyce remembered Sheehan's coined word and used it, though with a different meaning, in Ulysses. (1971, p. 23)
We do not know when Joyce picked up the word from Sheehan. Also, we have no contextual examples of Sheehan’s use from which to judge the meaning, though we have Stanislaus Joyce’s assertion that ‘he applied it to various statements and platitudes’.
Did Sheehan coin the word?
No. Aquacity had been used well before the early twentieth century, but only occasionally. There is little evidence of continuity of use over the centuries. Furthermore, it is a word that is easily re-inventable, based on Latin aqua ‘water’ and the (reasonably) common termination –acity (as in vivacity, loquacity, opacity, etc.), and so it is possible that many people ‘invented’ the word, each one thinking it was their own coinage.We can find early evidence for the word aquacity – meaning something like ‘wateriness’ or ‘watery nature or condition’ – in the seventeenth century. John Taylor (a Thames waterman who called himself the ‘Water Poet’) writes:
It was a poore mortified Liquor, having no vivacity left in it, but meerely cold, comfortlesse, and at the best, a poore decayed single-soal'd drinke, although it were dead, and a deceased remnant of humidious Aquacity.
John Taylor Taylors Feast (1638), p. 49
After this, the word’s appearance is patchy. It enjoys a short vogue in scientific texts in the seventeenth and eighteenth centuries,1 and crops up in the Victorian magazine Fun (13 September, 1873).2
There is evidence for its occurrence around the time of Joyce’s meeting with Sheehan in Dublin in 1909:
Just as we might give the name aquacity to the properties possessed by water, so we have actually given the name vitality [...] To be sure, vitality is more marvelous than aquacity, but so is protoplasm a more complex compound than water.
Herbert Conn The story of the living machine (1909), p. 80
But stronger evidence for its currency in Dublin comes from a racing report in the Irish Independent newspaper for 27 February 1908:
An Irish Day. A dismal drippy day at Warwick, the ‘ambient aquacity’ being relieved by the successes of Irish jumpers, of whom two were ridden by W. Taylor (jockey to the Winchester stable..), and three trained by Mr. J. J. Maher. (p. 3)
All of these usages are in the literal sense ‘wateriness’, ‘watery nature’, or ‘watery condition’. We are told that Sheehan used aquacity in an extended meaning, applying the thin, transparent, or insipid nature of water to ‘various statements and platitudes’. Perhaps that aspect was what Joyce regarded as Sheehan’s invention. Despite Stanislaus’s comment that his brother ‘used it [...] with a different meaning, in Ulysses’, the meaning Joyce employs – talking of ‘aquacities of thought and language’ – is not too distant from Sheehan’s use.
Whether Sheehan ‘coined’ the word or not, whether he imposed a new meaning on an existing word, or even whether he simply picked up a usage he’d heard in Dublin and passed it on to Joyce, the important point is that aquacity struck Joyce as an apt and significant neologism which he wished to weave into his narrative.
[For more biographical information on Daniel Sheehan see: “Daniel T. Sheehan: a University friend”.]