If I set up a custom taxonomy called Fashion and set up a top level term and some second level terms I get:
Top level term: Men
Second level terms: Bags, Shirts, Trousers
However, when I create a new top level term (let us say 'Women') and some second level terms - one of which is identical to a second level term I have already set up under 'Men' I get a slightly different URL
As you can see if you have duplicate second-level terms in a custom taxonomy WordPress doesn't like it very much and modifies the slug so that that second-level term is unique.
It would be great to be able to have both