A verb in the Quenya Verbal System (QVS) from 1948, glossed “creep” and based on the root ᴹ√SLIK of the same meaning (PE22/113). It also had a frequentative form lilhikke “sneak about”, indicating the base verb may mean “✱sneak” as well.
Qenya
illi
as many as
illin
pronoun. you (emphatic polite plural)
hlik-
verb. to creep, to creep, *sneak
The correlative ᴹQ. illi “as many as” appeared in Demonstrative, Relative, and Correlative Stems (DRC) from 1948 (PE23/111), a combination of the relative pronoun ᴹQ. i and ᴹQ. -lli(ni) “many”.
Neo-Quenya: For purposes of Neo-Quenya I would update this to ᴺQ. yallini “as many as” using the relative pronoun ya more commonly used in declined forms in later writings, such as Q. yassë “where [relative]”.