An unglossed root in The Etymologies of the 1930s glossed with derivatives ᴹQ. sikil/N. sigil “dagger, knife” (Ety/SIK).
Middle Primitive Elvish
dag
root. dig
dagwe
?. dagwe
dagdā
noun. pit
ndag
root. *slay
sik
root. *dagger, knife
(n)dak
root. slay
day
root. shadow
dak
root. slay
A rejected root in The Etymologies of the 1930s glossed “dig” (Ety/DAG), it may have been a transient replacement for √SAP.