The spelling of the word "trigonellites" can be quite tricky due to its unusual combination of sounds. In IPA phonetic transcription, it is pronounced as /traɪˌɡɒnəˈlaɪts/. The initial syllable "tri-" indicates three, followed by the sound /ɡɒn/ which blends with the "-i" to form the middle syllable. The final syllable, "-ettes", is pronounced as /ˈɛts/, which means small things. Therefore, "trigonellites" refers to small, three-sided objects and its spelling can be memorized by breaking it down into its distinctive parts.
In geol., a shell-like organism consisting of two plates or valves, and so called from its triangular form.
Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874.