In the other bed, the best, our guests dozed on,
dribbling their prose.
Here the speaker reveals the premise of this poem: the second-best bed could have been left to Hathaway because their best bed was their guest bed. This was, in fact, often the custom in Elizabethean households. This moment also shows what separated Hathaway and Shakespeare from the rest of the world: they lived through poetry and drama, while everyone else lived sluggishly in prose.
my body now a softer rhyme
to his, now echo, assonance; his touch
a verb dancing in the centre of a noun.
Here the speaker underscores the importance of poetry in the relationship between Shakespeare and Hathaway. She defines their relationship through poetic devices; those devices, echo and assonance, both deal with repetition as a vehicle for meaning. Duffy suggests that Hathaway is repeating her husband in a meaningful fashion, that she has learned through him the close relationship between eroticism and language. This suggests that Hathaway thoroughly understood her husband and emphasizes the significance of their relationship—not just to her, but to him as well. By metaphorically embodying "echo, assonance," Hathaway helps Shakespeare understand the poetic devices that were so important to his own work as a poet and dramatist.
By comparing her husband's touch to a "verb dancing in the centre of a noun," the speaker illustrates the liveliness of their intimate relationship. The verb is within the noun; this is one of the more sexually suggestive moments of the poem.
My living laughing love–
I hold him in the casket of my widow’s head
as he held me upon that next best bed.
Here, the speaker vows to keep their love the same in death as it was in life. Given the context of Shakespeare's will and the beliefs among historians it spawned about Shakespeare not loving his wife, this moment works to reassert the fullness of their relationship, and to remind the readers of the little they can know about it; it lives on only in the casket of her head.
‘Item I gyve unto my wief my second best bed…’
(from Shakespeare’s will)
The quote here is the epigraph of the poem; Shakespeare himself wrote this, not Duffy. By focusing on this moment and directly quoting Shakespeare's words, Duffy implicitly questions how the perception of Hathaway would shift had he left her a different item. The poem does not focus on that question, but its focus on the item in question shows how assumptions can be easily made from scant amounts of information.
There is something to be said about why this poem uses Shakespeare's words from a legal document instead of quoting any of his plays or poems, despite the clear significance of his creative writing to the narrator. This may be due to Duffy's wish to derive information from the factual evidence of Hathaway and Shakespeare's relationship, as those who say that the two did not get along claim to do. This poem is no more fanciful than any of those claims.