The Etymologies seem to list this word as a noun, but it is clearly the third person singular of the verb
Noldorin
lhâf
verb. (he) licks
lhav-
verb. to lick
blâb
verb. (he) flaps, beats
lhammas
noun. account of tongues
lhôd
verb. (he) floats
orthor
verb. (he) masters, conquers
osgar
verb. (he) cuts, amputates
síla
verb. (he) shines white
sôg
verb. (he) drinks
thia
verb. it appears
tôg
verb. (he) leads, brings
tôl
verb. (he) comes
According to WJ/301, the expression tôl acharn "vengeance comes" was later changed to tûl acharn by Tolkien
A noun appearing as N. lhâf “lick” (with Noldorin infinitive form lhebi) in The Etymologies of the 1930s from the root ᴹ√LAB of the same meaning (Ety/LAB) where the initial initial l was unvoiced to lh as was the case in Noldorin of the 1930s.
Conceptual Development: This verb was G. lav- “lick” in the Gnomish Lexicon of the 1910s (GL/53), clearly based on the early root ᴱ√LAVA since the unvoicing of initial l was not a feature of Gnomish in the 1910s.
Neo-Sindarin: Most Neo-Sindarin writers adapt this word as ᴺS. lav- “to lick” since the unvoicing of initial l was also not a feature of Sindarin in the 1950s and 60s.