Final answer:
The word 'halcyon' means calm and peaceful, similar to tranquil or unruffled. It does not mean troubled or tumultuous. 'Halcyon' days refer to times of peace and serenity, much like a calm sunset by the river.
Step-by-step explanation:
The word 'halcyon' refers to a period of time that is idyllically calm and peaceful. Option 1) Tranquil and option 2) Unruffled both correctly capture the essence of 'halcyon.' The term originates from a mythological bird, the halcyon, which was said to calm the waves of the sea during its nesting period, thus leading to the association of the word with calm and peaceful times. Conversely, options 3) Troubled and 4) Tumultuous are not correct as they denote disturbed or chaotic states which are the opposite of halcyon. The serene imagery evoked through phrases like 'river and sunset and scallop-edg'd waves of flood-tide' aligns well with the meaning of 'halcyon' as they convey a sense of peace and tranquility.