The first occurrence.
In the beginning created God Elohiym את the heaven and את the earth. Gen 1:1
(In the year that King Uzziah died, and I saw את the Lord Adonai sitting on a throne … Isa 6:1)
The primitive root.
Strong’s H853 את aith, an untranslated particle indicating a reflexive: “In the beginning created God Elohiym את Himself …” The aleph-tav is from Strong’s H226 oth, a concrete noun meaning, “mark, sign;” from Strong’s H225 אות uwth, a primitive root meaning, “to consent.” The 3-letter root is aleph + vav + tav.
aleph א = the ox head, thus strength, power, leader
vav ו = the 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.