Identifying the different word from a group of words is a common type of question in various competitive exams. Let's analyze the given options to understand why 'Hireling' is the odd one out.

Different meanings:
- Calf: a young cow or bull
- Cub: a young bear, fox, lion, etc.
- Piglet: a young pig
- Duckling: a young duck
- Hireling: a person who is hired to do a specific job or task

As we can see, all the options except 'Hireling' refer to young animals of different species. On the other hand, 'Hireling' refers to a human who is hired for work. Therefore, 'Hireling' is the odd one out as it doesn't belong to the same category as the others.

Different suffixes:
- Calf: ends with 'lf'
- Cub: ends with 'b'
- Piglet: ends with 'let'
- Duckling: ends with 'ling'
- Hireling: ends with 'ling'

One could argue that all the options end with '-ling,' but that wouldn't prove that 'Hireling' is not the odd one out. Instead, we can observe that the suffixes of the other options (-lf, -b, -let) are different from each other. However, the suffix '-ling' is common to both 'Duckling' and 'Hireling.' Therefore, the suffix analysis doesn't help us to identify the odd one out.

Different associations:
- Calf: associated with cows and bulls
- Cub: associated with bears, lions, foxes, etc.
- Piglet: associated with pigs
- Duckling: associated with ducks
- Hireling: associated with employment, work, and job

Again, we can see that 'Hireling' doesn't belong to the same category as the other options. All the other options are associated with animals, whereas 'Hireling' is associated with employment and work. Therefore, 'Hireling' is the odd one out.

In conclusion, we can say that the correct answer is option 'E' - Hireling. It doesn't belong to the same category as the other options as it refers to a human who is hired for work, whereas the others refer to young animals.