port-sider, n. — Green’s Dictionary of Slang

port-sider n.

[naut. imagery; port, the left-hand side of the boat]

(US) a left-hander.

1919		C.E. Piesbergen Overseas with an Aero Squadron 66: ‘Lefty’ he was called because he was a port-sider.
1930		R.E. Howard ‘Waterfront Fists’ Fight Stories Sept. 🌐 He was the first good port-sider I’d ever met in a ring.
2002		‘Weir belongs among the elite’ on MSNBC News 13 Apr. 🌐 He is no longer another lefty, he’s the only lefty, the only lefty to win a Masters. [...] He’s the only lefty a right-hander need remember when he has the urge to tease the port-sider playing in his foursome.