Main Entry:
gang·way Pronunciation: 'ga[ng]-"wA
Function: noun
Date: before 12th century
1 : PASSAGEWAY; especially : a temporary way of planks
2 a : either of the sides of the upper deck of a ship b : the opening by which a ship is boarded c : GANGPLANK
3 British : AISLE
4 a : a cross aisle dividing the front benches from the backbenches in the British House of Commons b : an aisle in the British House of Commons that separates government and opposition benches
5 : a clear passage through a crowd -- often used as an interjection I know nothing about boats, either, so I'm guessing here, but wasn't it common to yell "Gangway!" on a ship when you wanted to let someone know you were coming along the gangway, in a hurry, and they better move their ass?
I'm guessing this phrase originated in WWII, and just slipped into the national lexicon . . .
No fucking clue what "gainway" is, though . . .