Theory:

Meaning of difficult words from the poem "A Slumber Did My Spirit Seal":
 
S.No
Words
Meaning
1
SlumberDeep sleep
2
SealFasten securely
3
SpiritThe non-physical part of a person which is the seat of emotions and character
4
Earthly yearsThe passing time and seasons in Earth
5
DiurnalPertaining to happening daily
6
ImpliedIndirect or hidden
7
MelancholyExtreme sadness
8
NumbHaving no feeling or emotions
9
DepartTo leave or exit
10
PangsThe pain that one experiences
11
FragmentsBroken pieces of a whole substance
12
CharismaEnthusiasm or charm