A neologism for “pay back” coined by Helge Fauskanger for his NQNT (NQNT) as a combination of nan- “back” and [ᴱQ.] paitya- “repay”.
Primitive elvish
pay
root. punish, take vengeance on, requite; conquer, subdue
kayan
root. ten
kway
root. ten
kwayam
cardinal. 10
A root Tolkien introduced in the late 1960s as the basis for his latest Elvish word for “ten”: Q. quëan/quain, S. pae, T. pai(n) (VT42/24; VT48/6). It was an extension of √KWA “complete” as in “a complete set of (10) fingers”. Prior this late change, the usual word for “ten” was ᴹQ. kainen (along with other variants beginning with kai- or kea-) from the root ᴹ√KAYAN or ᴹ√KAYAR as it appeared in The Etymologies of the 1930s (Ety/KAYAN). This basis for “ten” dates back to the Early Qenya Grammar of the 1920s (PE14/49, PE14/82). Tolkien was still considering √KAYAN for “10” in the late 1960s before replacing it with √KWAY(AM) (VT48/12).