A root introduced by Tolkien in Definitive Linguistic Notes (DLN) from 1959 with the gloss “close eyes, blink, wink” to provide a new explanation for the flower name S. alfirin (originally “immortal = not mortal”) after he decided the prefix al- meant “well” rather than “not” (PE17/146). He derived the names Q. pirindë and S. pirin for “a flower that opened and shut quickly with any change of light”. The root ᴱ√PIRI also appeared (unglossed) in the Qenya Lexicon of the 1910s with derivatives like ᴱQ. piri- “spin, turn”, ᴱQ. pirin “thin rod, pin” and ᴱQ. piruke “swirl, twisting, pirouetting” (QL/74). Finally, the word Q. pirë “toe” appeared in notes associated with the 1955 version of the poem Q. Nieninquë, perhaps representing a third meaning for this root (PE16/96).
Neo-Eldarin: For purposes of Neo-Eldarin, I think the gloss “blink, wink” for √PIR is not a great fit, since it is a contrived etymology Tolkien invented for a word he clearly meant to be something different originally. Q. tihta- is probably a better known verb for “blink”. For “spin”, I prefer a Neo-Eldarin root ᴺ√KWIR adapted from early ᴱ√QIŘI. However, I think ᴺ√PIR might be retained as a Neo-Root with the sense “✱cylinder”; I think this works as an explanation of Q. pirë “toe”, and allows the retention of early words like ᴱQ. pirin “thin rod, pin” and ᴱQ. pirinumbe “cylinder”.
pir- "spin, turn" (apparently intransitive). Actually cited in the form piri-, perhaps with the connecting vowel of the aorist included. "Qenya" pa.t. pírë. (QL:74)