the.com/greeting

A two-second ritual that decides whether a stranger becomes a friend or a story.

means A word, gesture, or message used to acknowledge someone when you meet or address them.

from From the Old English verb 'grētan,' meaning to approach, accost, or salute — to come up to someone with intent. The same root surfaces in German 'grüßen,' a likely Germanic cousin. Originally the act could be hostile or friendly alike: to 'greet' an enemy was simply to confront them. Over centuries the meaning softened from any approach into the specifically warm hello we know now, with the '-ing' marking it as the thing itself rather than the doing.

handshake origin: Possibly proved empty hands held no weapon
global variety: Some cultures press noses, others spit politely
hello's age: Popularized by the telephone, not conversation
primate roots: Chimps greet with hugs and palm-grasps
brain speed: First impressions form in under a second

for instance

hawaiian lei greeting — traditional welcome in hawaii where garlands of flowers are placed around visitors' necks

maori hongi — new zealand indigenous greeting where two people press foreheads and noses together

thai wai — respectful greeting in thailand where hands are pressed together at chest level with a slight bow