Well, some preliminary thoughts.
First of all, it'd be absolutely crucial for an alliance of Populists, the Farmers Alliance, and the Knights of Labor to also bring in the Socialist Labor Party. First off, the SLP has considerable human resources among the immigrant populations of the major cities. Alliances between them and the more native groups would be crucial to stopping them from shooting themselves in the foot with nativism. Second, the SLP is a conduit for effective, experienced activists from Europe to enter the American movement.
Second, the inclusion of the IWW is anachronistic; the IWW wasn't founded until 1905, and it was formed by AFL dissidents from the anti-political, business unionism of Samuel Gompers, as well as from the ashes of the SLP's Socialist Trade and Labor Alliance. ITTL, no IWW would ever form, because presumably the Knights of Labor would organically involve into an industrial trade union. Probably be something like "Trade Union Congress" or if they wanna lean on the founders, the "Continental Congress of Labor".
As for what the resulting amalgamation would be named, I'm inclined to think it would be something simple. Probably not Agro-Industrial Populist. Farmer-Labor seems to be the most likely outcome if it's a more or less equal union between urban trade unionists and Marxists with rural populists. Though, historically, "Socialist Party" was apparently good enough to capture both demographics, though at a slightly later date.