As tough as old boots and Hard-boiled

Hard-boiled and as tough as old boots are semantically related In some cases you can use "Hard-boiled" instead an adjective phrase "As tough as old boots".

Hard-boiled adjective - Having or showing a lack of sympathy or tender feelings.

As tough as old boots and hard-boiled are semantically related in hard-nosed topic. You can use "As tough as old boots" instead an adjective phrase "Hard-boiled".