A root in The Etymologies of the 1930s glossed “day” with various derivatives like ᴹQ. are, N. aur “day” and ᴹQ. arin “morning” (Ety/AR¹). In Tolkien’s later writings, the Quenya word for “day” became aurë (RC/727; S/190), and in 1957 Quenya Notes he devised a new etymology for these day-words from the root √UR “heat” as in ✶auri “heat, period of sun” (PE17/148). That opens the question whether the various 1930s Quenya “morning” words from ᴹ√AR remain valid, but many Neo-Quenya writers (including me) retain them since there aren’t really any good alternatives. They might be salvageable as derivatives of the later root √AS “warmth” (so that “day” = “hot” and “morning” = “warm”).
Middle Primitive Elvish
rē/ere
root. bear, produce
ar
root. day
ari
noun. day
A root appearing as {GERE/GRÉ >>} ERE/RÉ “bear, produce” in drafts for the first version of Quenya Personal Pronouns (QPP1) from the late 1940s, contrasted with masculine ᴹ√NŌ/ONO “beget” (PE23/87 note #85). In these rejected notes, RÉ was the basis for various feminine adjectives and NŌ the basis for various masculine adjectives. Elsewhere √NŌ was not specifically masculine, so I think this was a transient idea.