Hence
Thus, consequently, for this reason; OR a time in the distant future
Reverence
Awe, admiration, deep respect
Birdseye
Reference to Clarence Birdseye, 1886–1956, an American inventor of the food-freezing process, and a businessman. This usage is perhaps a pun on the word “birds-eye,” which means a view from above (panoramic) OR hasty and superficial.
Scholar
Combined with the term Birdseye, scholar takes on the meaning of an expert or aficionado. Clarence Birdseye learned enough about how to freeze food that he invented and put in place a system that revolutionized consumption and is still used today.
Sole
Being the only one, one of a kind, lonely or exclusive. Can also mean functioning automatically or with independent power. Lastly, sole is a type of fish. This may be a pun by MacLeish, because grammatically it's more likely that he means "one of a kind" in the context of the poem (though the poem references salmon).
"To be, yes"
A reference to Hamlet’s speech in William Shakespeare’s play Hamlet, in which he ponders whether it is better to live or die in the face of adversity. The most famous part is: “To be, or not to be, that is the question: / Whether 'tis nobler in the mind to suffer / The slings and arrows of outrageous fortune, / Or to take arms against a sea of troubles / And by opposing end them.” In this poem, MacLeish is answering Hamlet's question and affirming the choice “to be”; to live.
