Trissyllable

Which when ſubſcrib’d writes Legion, names on Truſs, / Abaddon, Belzebub, and Incubus, / All the Vice-Royes of darkneſs, every ſpell / And Fiend wrap’d in a ſhort Triſſyllable.

Source: wiktionary

And tho’ this would not be the Primitive Language for which it was made, yet for the preſent uſes of it (the chiefeſt of which is the aſſiſting and refreſhing the memory, and helping the imagination by proper ſounds) it might be as good: wherein the ſingle Characters might be Monoſyllables and the compounded diſyllables [Diſſylables in https://books.google.com/books?id=MpowAAAAYAAJ&pg=PA231] Miscellanea Curiosa, 1707 triſſyllables, &c.

Source: wiktionary

In reading dissyllables, trissyllables, &c. it will be easy for teachers to make their scholars understand, that instead of the division, they should substitute the simple or articulated sound which is represented by the letters that are annexed to it, and read the word all together: and that these divisions are inserted only for the sake of facilitating the syllabisation, if I may be allowed the expression.

Source: wiktionary

The Greeks have nowhere, as we have seen, complained of any difficulty in associating their dissyllables, alpha, beta, gamma, delta; and trissyllables, omicron and omega, with the elements of sound to which they refer.

Source: wiktionary