The idea of labor aristocracy goes back to pre-Marx, where it was used to explain why the English trade unions failed to radicalize and could in fact be pretty reactionary and imperialist. The idea was that while they are proletarian in their relationship to production (the labor part), they receive so much gain from imperialism (along with social status) that they fail to become globally class conscious. Instead, they support their country's imperialist wars that bring home the loot they split with their bourgeoisie.

This is reminiscent of US labor that was "bought off" by similar means a century ago and many of the remaining industrial unions in the US. Those for military contractors are the most obvious, but a lack of global class consciousness can be found in almost every union here. Knee-jerk support for other unions kicks in, so you'll see Teamsters and SEIU and UAW supporting Boeing workers next year despite the latter making the tech that eventually spies on Gazans and bombs kids. And in only one of the above is there a subculture that I'd call class consciousness (UAW via UAWD). Try having conversations about socialism in these unions and you'll have to scrounge for even basic class consciousness and might get hounded out by staff. The classism I mentioned earlier is rife in two of those big unions.

This is something we have to recognize if we want to rely on a labor strategy as socialists in the imperial core. I've seen a lot of socialists with very little labor experience but rose-tinted glasses about labor militancy from the late 1800s run head-first into union organizing and then becoming dismayed at what they find when they stop looking for the "corrupt union bosses" as the only ill. And those socialists that are anti-imperialist will quickly find that labor-focused socialists tend to be imperialist, as their efforts do tend to be in support of the conditions of a better-off subset of the imperialist working class. Try telling them to have a slightly critical approach to the Teamsters, who are both militant and reactionary. They'll start to get scared they'll lose what little labor connections they have (not a false fear).

Anyways, that's the old-school concept of labor aristocracy and also more or less the same concept used by MLs and Maoists when they want to look at this problem. It's an attempt to provide a material interest rationale for why the imperial core trade unionists almost always suck at class consciousness, especially anti-imperialism.