Tolkien used the word Q. ve for “as, like” in Quenya for much of his life, but its etymological origins varied. In the the Qenya Lexicon of the 1910s, Tolkien had two distinct roots for “similarity”: unglossed ᴱ√SĒ with variant ᴱ√SENE⁽²⁾ and derivatives like ᴱQ. se “as, like, in manner of” and ᴱQ. (a)sesta- “to liken, compare” (QL/82), and also ᴱ√VĪ “as” with variant ᴱ√VI‘I and derivatives like ᴱQ. ve “as, like”, ᴱQ. vealta- “to resemble”, and ᴱQ. vīkana- “compare” (QL/101). The semantic distinction between the two roots isn’t clear, and in the contemporaneous Gnomish Lexicon there was a third set of forms beginning with fel- such as G. fel “as, like”, G. feleg “equal”, and G. feltha- “resemble, seem like” (GL/34).
In later notes Tolkien proposed a variety of primitive origins for Q. ve “as, like”: ✶wē (we’e) in 1957 Quenya Notes (VT49/10; PE17/189), ✶bē from notes from the late 1950s or early 1960s (VT49/32 note #10), and ✶vai as a relative of suffixal -va in notes from 1968 (VT49/32 note #10). As there are not any definite Sindarin cognates for Q. ve in Tolkien’s published writings, it is hard to know which of these is more likely.
Neo-Eldarin: For purposes of Neo-Eldarin, I would go with primitive ✶bē as the most widely excepted option, producing S. ✱be “as, like”.
A root in notes from the late 1960s glossed “glide, slide, slip, drip” where it served as the basis for primitive ✶linkwē for “light” as an ethereal and liquid-like substance (NM/283). The Quenya word Q. linquë had a similar meaning, but Sindarin S. limp “(bright/clear/gleaming) liquid” was used of used of pools or rills of clean water, and so served as an element in the name S. Limhír (†Limphîr) “Limlight” (NM/284).