The story
From riding + association.
Etymology from Wiktionary, CC BY-SA 4.0.
Today it means: A local wing of a federal, provincial, or (in Yukon) territorial political party, consisting of the members of the party living in one riding, legally recognized by the relevant electoral authority, and conducting local partisan actions such as nominating the party's candidate for elections. Full definition →
From riding + association.
Etymology from Wiktionary, CC BY-SA 4.0.