Neologism! This text is a neologism, which means that it was not composed by Tolkien himself. The content presented herein should therefore always be considered as experimental and subject of debate.
Consider Elaran the author of this work.
A more plausible alternative to a problematic yet often used Neo-Sindarin phrase.
The phrase **hannon le comes from the Lord of the Rings film trilogy. David Salo, the linguist who prepared the Quenya and Sindarin material for these films, reconstructed the verb **hanna-, "to thank", probably about 18 years ago. But the story of this reconstruction goes back to 1980, to the publication of the Unfinished Tales. In this book, we see the word Eruhantalë with its meaning given as "Thanksgiving to Eru", and it would be safe to assume that hantalë means "thanksgiving" by itself. It is also rather clear that the final element of this word is the abstract noun suffix, -lë, which Quenya is known to employ and form nouns from verbs. Thus, we reach the Quenya verb hanta-, meaning "to give thanks".
This is, I assume, how Salo worked at the time: We have the Quenya verb, so we are ready to reconstruct it for Sindarin. This means that we will use the phonetic development rules that concern Sindarin (rather than Quenya) as we derive it from Primitive Quenderin. But in the early 2000s, we had no documents in which a root word for this verb was shared. Then we need to guess what its root may be, and √KHAN seems to support it phonetically, despite its unfitting meaning "to understand". Having almost no other option, we employ this root and assume that it might have had a semantic shift during its journey to Sindarin. Now, without going into great detail on the development stages: Ancient kh- is found as h- in both Quenya an Sindarin: √KHER > Q. heru / S. hîr . And the medial NT in Quenya words is often found as -nn- in Sindarin: Q. panta- / S. panna-. In conclusion, given the lack of attested material at the time, reconstructing Quenya's hanta- as Neo-Sindarin **hanna- was an arguably safe approach. However, in January of 2002, the 43rd issue of Vinyar Tengwar shared this word's root as √HAN, and this is where the problems arise, since we also have this:
PQ h- only survived in the dialects of Aman. It disappeared without trace in Sindarin. [HoME-XI/365]
If this word's root is √HAN, and if h- disappeared in Sindarin, then our verb must be *anna-. This may also be problematic, because we already have anna- attested as "to give". But then comes the 22nd issue of Parma Eldalamberon to share some of Tolkien's latest ideas, offering the Telerin verb han- as "to give". More importantly, the gerund of Sindarin's "to give" was shared as aned, suggesting that Tolkien perhaps updated this verb to an-, derived from √HAN like its Telerin cognate. And so we realise that it may in fact be plausible to use anna- as "to give thanks".
Now, we may attempt to use it in a phrase to say "thank you". For this, we would need "you" in dative form (which may not be le as used in Salo's phrase), but this is also a matter on which we have little information, and there is no consensus in the communities concerned with Tolkienian Linguistics about how to approach this issue. Again, without going into great detail, I propose to use *allen as "to thee", based on the attested phrase ón annin and other analogues. Thus, we get:
I give thanks to you!
Please keep in mind that this is not an "absolutely correct" form of giving thanks in Sindarin, but it is indeed a better alternative to **hannon le which even Salo would now admit to be erroneous. As such, this new phrase, along with all other works in Neo-Sindarin, are subject to change by default, until their direct attestation in the posthumously published works of Tolkien which are currently being edited by the Editorial Team of the Elvish Linguistic Fellowship.