Because I had the time today to explore the etymology/roots for this Lesson 22 passage and I was curious (this language is hauntingly beautiful to me … thanks @Karuna_Hong for the inspiration on root study):
gambhīrā is the name of a river in India that may be the source for the pāli meaning here – there is no sanskrit root other than the full name of the river.
paṇītā is rooted to nī, meaning to lead or carry. I wonder whether there’s a sense of carrying a flavor forward in the palette, as the sublime meaning (in English) may infer the sublime deliciousness of food(?).
atakkāvacarā is a bahubbīhi compound where, according to DPD, the frequency is quite low in the suttas, as is the case for the words avacara and takka (although takka appears much more in the commentaries per DPD). This was curious to me.
nipuṇā is rooted to puṇ thus conveying a sense of subtlety related to skillfulness or piety.
This little digression helped reinforce the meanings of those particular terms.
Unless I’m off-track! John or Stephen (or anyone else), please correct me as needed 
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