A root in the Qenya Lexicon of the 1910s glossed “steal, take; get by stealth, unlawfully”, with derivatives like ᴱQ. nak (naq-) “anything stolen, a theft, a trick” and ᴱQ. naqar “thief” (QL/64). There are no signs of this root in the contemporaneous Gnomish Lexicon, but words like G. nig- “steal, creep, do or go by stealth” and G. nigla- “to thieve, pilfer” might be derived from a variant (GL/60); there is otherwise no ✱ᴱ√NIKI root appearing in the Qenya Lexicon. There are no signs of either of these roots in Tolkien’s later writing with these meaning; later √NIK means “small” (VT47/26; VT48/18).
Early Primitive Elvish
taka
root. fix, fasten, stick
paẏa
root. requite, punish, take vengeance on, conquer, subdue
naqa
root. steal, take; get by stealth, unlawfully
vḷtḷ
root. release, set free; deprive, take away
A root in the Qenya Lexicon of the 1910s glossed “release, set free; deprive, take away” serving as the basis of the suffix ᴱQ. {-velte >>} -vilte or -valta “less” (QL/102). Its equivalent in the contemporaneous Gnomish Lexicon was G. -(a)vlid where the primitive form was given as vḷt (GL/23). There are no signs of this root in Tolkien’s later writing.
tuv-
verb. to receive, take
mapa
root. seize
mapa-
verb. to seize
maha
root. grasp
nap-
verb. seize
A root in the Qenya Lexicon of the 1910s glossed “requite, punish, take vengeance on, conquer, subdue”, with derivatives like ᴱQ. paime “the vengeance taken, the punishment, the penalty; an infliction” and ᴱQ. paitya- “repay, requite” (QL/72), along with augmented forms like ᴱQ. apaika “conquering” and ᴱQ. apaire “victory, conquest, reduction” (QL/34). G. abair “victory” from the contemporaneous Gnomish Lexicon was almost certainly related (GL/17). The root ᴹ√SPAY “despise, contemn” from The Etymologies of the 1930s might also be related (Ety/SPAY).
Neo-Eldarin: For purposes of Neo-Eldarin, I think this root might be salvaged as ᴺ√PAY “punish, take vengeance on, requite” to serve as the basis for Neo-Quenya words for vengeance and punishment.