ᴹ√STAK root. “split, insert”
A root in The Etymologies of the 1930s glossed “split, insert” with derivatives like ᴹQ. sanka/N. thanc “cleft, split” and N. nestegi “insert, stick in” (Ety/STAK). S. thanc remained an element in S. Orthanc “Forked Height” (LotR/555; UT/400), indicating the ongoing validity of this root.
References ✧ Ety/STAK; EtyAC/NDAK