The oath was an institution of fundamental importance across an enormously wide range of social interactions throughout the ancient world. Oaths were uttered, prescribed, or referred to in almost every kind of literary or inscriptional text we have from the archaic world. This fundamental importance shows why the word was remembered with such accuracy and carried over into descendent cultures.

English - Oath

= a solemn pronouncement to affirm the truth of a statement.

Hebrew - אוּת - awth

= sign, mark, token, ensign, standard, miraculous sign, proof, warning, consent and agreement.

Family/Language I-E Reflex(es) Gloss
Middle Irish: oeth oath
Welsh: arfoll oath
Old English: awth oath
  awth-brice perjury, lit. oath-breaking
  awth-gehawt sacred pledge, lit. oath-vow
Middle English: ooth oath
English: oath

calling upon God

to witness to truth

Old Frisian: eth/ed oath
Dutch: eed oath
Old Saxon: aith oath
Old High German: eid oath
Middle High German: eit oath
German: eid oath
Old Norse: eithr oath
Danish: eed oath
Swedish: ed oath
Gothic: aiths oath
Latin: iuro oath
Portuguese: juramento oath
Spanish: juramento oath
French: serment oath
Italian: giuramento oath
Greek: orcos oath

From TWOT:

Owth is the general word for "sign," and it covers the entire range of the English term and the Greek word semeion. On the pedestrian end of the scale it includes what amounts to a "signboard" or "standard" (Num 2:2). It also includes such important concepts as the rainbow "sign" to Noah (Gen 9:12-13,17).

1. ‎Owth ‎first occurs in Gen 1:14, where it refers to the luminaries serving as "signs" to distinguish the seasons. In Jer 10:2 it has a similar meaning.

2. According to Gen 4:15, the Lord set a "mark" on Cain. The meaning of this word is uncertain.

3. A third use of the word is illustrated by Gen 9:12-13,17; according to which the rainbow is a "sign" of the covenant. Circumcision is the "sign" in Gen 17:11. Also, the Sabbath is to be a "sign," according to Ex 31:13,17 and Ezek 20:12. It is this use of "sign" that is meant when Christians refer to the ordinances as outward "signs" of inward grace.

4. Most of the eighty occurrences of ‎owth ‎refer to "miraculous signs." All the plagues on the Egyptians are called "signs." In these contexts the complementary word ‎mopet ‎(q.v.) meaning "wonders" often occurs (Ex 7:3; Deut 4:34; 6:22; 7:19; 26:8; Neh 9:10; Isa 20:3; et al.). This word ‎owth ‎is used in Isaiah's famous prophecy to Ahaz (Isa 7:11,14). The shadow's advance on the palace steps was a "sign" for the ailing king Hezekiah (2 Kings 20:9; Isa 38:7). Likewise God showed Gideon a "sign" by igniting the offered food (Judg 6:17).

5. The word ‎owth ‎sometimes means "token." For example, Aaron's rod was to be a "warning to the rebellious" (17:25 in the book of Numbers NAB and Heb, v. 10 in other English versions). In the same category are the stones in the Jordan (Josh 4:6), the hammered plates on the altar (Num 16:38), and the witness pillar in Egypt (Isa 19:20).

6. A dreamer or a prophet, true or false, could produce "signs" according to Deut 13:1ff The fulfillment of Jeremiah's threat of punishment was a true "sign" (Jer 44:29), while Isaiah speaks of "signs" of liars (Isa 44:25).

Naturally, these categories are artificial and overlap, The simple fact that one Hebrew word covers them all is proof of that. The word "sign" either signifies the unusual event itself or in someway points to that unusual event. Or it may point backward to a historical event such as the stones in the Jordan (Josh 4:6), or even forward to such a promise as a thornless future world (Isa 55:13).