Final answer:
The speaker refers to the word 'son' to emphasize the emotional connection and care between the speaker and the person being addressed.
Step-by-step explanation:
The speaker refers to the word 'son' in the second line of the poem to emphasize the deep emotional connection between the speaker and the person being addressed. By using the term 'son,' the speaker establishes a familial relationship, suggesting that the person being referred to is not only a comrade in battle but also someone the speaker cares for deeply, like a son. This choice of language adds a layer of vulnerability and tenderness to the poem.