the.com/main
The principal artery of anything — water, code, or story — where the real flow lives.
means The chief or most important thing: a primary pipe, a central program function, or the headline event.
from From Old English maegen, meaning strength or power, later shrinking to simply the biggest, most important one of whatever you're counting.
Programmer's gateMost programs begin executing at main().
Plumbing rootThe main carries water before pipes branch off.
Old strengthOriginally meant might, as in might and main.