The Hebrew word for to forget is ַלִשְׁכּוֹח
, as in the Biblical context of agricultural gifts to the poor:
וְשָׁכַחְתָּ עֹמֶר בַּשָּׂדֶה…
and should you forget a bundle (of grain) in the field…
It’s a simple verb of the root שׁ.כ.ח (sh.k.kh).
A couple of other applications of this word and root include:
ַלִשְׁכּוֹחַ וְלִסְלוֹח
to forget and forgive
and
בִּלְתִּי נִשְׁכַּח
unforgettable