Agreed...the booklet makes that clear in a later chapter.
Far from being "morphed" by "Rome" the Latin word used by Catholics is ecclesia - a direct transcription of the Greek word.
Hence the Spanish word iglesia, the Italian word ecclesia, the Portuguese word igreja, the French word eglise, the Gaelic word eglaise, the Polish word kosciol, etc.
The word "church" is a Germanic one, and is of contested origin - some supporters of the Reformation have argued that it comes from kuriakh in the Greek phrase ekklesia kuriakh, that is "the Lord's assembly."
That's disputed and there are various theories as to why the Germanic languages, as opposed to the Romance and Celtic languages, adopted this word (church/kirche/kirk) instead of some form of ecclesia.