A rarely used prepositional equivalent of -llo (VT49/24; EtyAC/LŌ). In one note from 1969 Tolkien said “lō̆ as independent word was used only with person; thus not Manwello but lo Manwe, and usually in sense ‘by agent’ (VT49/24)”. As an example Tolkien gave the phrase nahtana lō Turin, apparently meaning “slain from [by agency of] Turin”. I interpret this to mean ló can only be used with animate beings, and no longer means “away from” by rather “by agency of”.
Conceptual Development: In The Etymologies of the 1930s lō was given as a derivative of the “ablative element” ᴹ√LŌ (EtyAC/LŌ).
yé (1) interjection "lo!" (VT47:31), also occurring in Aragorn's exclamation when he found the sapling of the White Tree. (Compare yéta-.) Also in the ejaculation yé mána (ma) = "what a blessing" or "what a good thing!" (VT49:41). The more literal meaning would seem to be *"behold the blessing!"