From ねた (neta) + 潰(つぶ)し (tsubushi, “連(れん)用(よう)形(けい) (ren'yōkei, “stem or continuative form”) of the verb 潰(つぶ)す (tsubusu).”).
ねたつぶし or ネタつぶし • (netatsubushi)