Here is an example Python program that accomplishes this task:

```python
import random

word_list = ['apple', 'banana', 'orange', 'watermelon', 'pineapple']

samples = []

for word in word_list:
    for i in range(len(word)):
        samples.append(word)

sampled_word = random.choice(samples)

print(sampled_word)
```

In this program, we create a list of words called `word_list`. We then create an empty list called `samples` to hold our samples. We iterate through each word in `word_list`, and then iterate through each letter in the word. For each letter, we append the full word to `samples`. This means that longer words will be added to `samples` more times than shorter words, increasing their chance of being chosen.

Finally, we randomly choose an element from `samples` using the `random.choice()` function and print the result.
Scrivete un programma che campiona casualmente da un elenco di parole. Più lunga è la parola, più dovrebbe essere campionata.