The first occurrence.
And God set them in the firmament of the heaven to give light on the earth, Gen 1:17
The primitive root.
Strong’s H853 אתם otam; a primitive pronoun for the 3rd person plural. It is contracted from Strong’s H226 אות oth, a concrete object meaning, “mark, sign;” as the untranslated aleph-tav; an untranslated particle indicating a reflexive: “In the beginning created God את Himself …” The primitive root is Strong’s H225 אות uwth, meaning, “to consent.” The aleph + vav + tav makes the parable.
aleph א = ox head, thus strength, power, leader
vav ו = tent peg, thus add, secure, hook
tav ת = crossed sticks, thus mark, sign, signal, monument
The story: As an ox (aleph) is driven toward (vav, as a tent peg is driven into the ground to secure the tent) a landmark (tav) in order to keep the plow furrow straight, so a powerful security (aleph + vav) marks (tav) the agreement of two parties to the covenant.
The 1st occurrence is Genesis 1:1. It’s in the verse twice.