Herculean describes a job or effort that needs huge strength or stubborn determination — clearing a whole street after a typhoon, sitting through a mountain of homework without giving up. It comes from Hercules (Heracles in the Greek stories), the hero who had to finish twelve almost impossible labours: cleaning vast stables, holding up the sky for a time, and so on. You may still see it with a capital H (Herculean), because it is from a name; though actually many writers now leave it small (herculean), as if it were an ordinary adjective like “huge.” It is a colourful, slightly literary word. In everyday speech people more often say “huge,” “back-breaking,” or “a massive job.” It does not mean “about the myth” unless the rest of the sentence is clearly about the hero; it means “as hard as one of his jobs.” And it is about the size of the effort, not about visible muscles: a quiet person can do herculean work at a desk.