Definition from Wiktionary, the free dictionary
yester- + morn
- (obsolete) Yesterday morning.
1816, Jane Austen, Persuasion:
- The sad accident at Lyme was soon the prevailing topic, and on comparing their latest accounts of the invalid, it appeared that each lady dated her intelligence from the same hour of yestermorn […] .
1826, Mary Shelley, The Last Man:
- "That, Clara," I said, "is the gate, that the street which yestermorn your father rode up."
1900, Rudyard Kipling, The Seven Seas:
- By the wisdom of the centuries I speak-- To the tune of yestermorn I set the truth-- I, the joy of life unquestioned--I, the Greek-- I, the everlasting Wonder Song of Youth!